[Closed] Petrol or diesel?

Sbob, you're taking the whole STW-dick thing to new levels.

If you want peak power delivery in a very tight rev range then go ahead, I prefer mine over a wider spread (power being the product of torque and rpm - work it out) for reasons I've already identified.

As for the Grandad statement I wasn't slating Hondas, I was merely using them as a very good example of engines that require a lot of work to keep them at their peak power. If you actually knew what you were talking about you would realise this (hence why a stock Type-R has less torque than my ancient diesel but far more power; again, torque x rpm).

I find it amazing that people moan about the power bands and noise. FFS talk about picky.

Why? I like the noise that multi cylinder petrol engines make. The 330 sounds lovely on start up and at the red line. My diesel sounds, er awful. Even the big BMW six derves don't sound particularly pleasant to me.

My diesel dumps all of its power in a narrow band of revs and then just gets louder. At least petrols give you a bit of an option.

Both have benefits. Personally I love the torque of a diesel combined with mpg.

I am running a diesel, 0-60 in 5.4 sec and 45mpg - cannot grumble!

My MX5 doesn't have much power. 143hp, 126 lb/ft of torque from a 1.8 NA petrol. 32 mpg-ish

Wouldn't want a diesel in it though, ugh.

Diesels are for people dead on the inside.

Why? It's a car not a lover. Honestly, it's not that big of a deal.

My diesel doesn't have a narrow power band. And the next person who posts up dyno graphs of engine speed vs power or torque gets a dirty look.

Why? It's a car not a lover. Honestly, it's not that big of a deal

But some people actually like cars and things like the noise they make....if I'm paying money for a car, I'd much rather do so for something that I like and can get a little bit interested in. You can't drive quickly etc these days, so whats wrong with having something that sounds a bit cheeky (or very cheeky in the case of a C63)? I'd rather that than listen to a broken Massey Ferguson.

"Diesels are for people dead on the inside."

diesel or petrol - if they are inside me in any great quantity im dead as a can of spam that much is a given.

seriously its a conveyance of people and shit from A to B on public roads.i really dont care how much the road is brought to life by coming on cam or hitting turbo..... 8v non turbo diesel FTW.

stick yer C63 anyway - industrial injection cummings 6BT would be cheeky enough for me - propper throaty sound none of this bzzzzzzzz that the c63 makes - although ill admit , pops and bangs the c63 gives on overrun are amaizing - 13mpg average isnt - nor is 1800 quid composite(steel alu) front disks.

so whats wrong with having something that sounds a bit cheeky

Fuel consumption? It don't grow on trees, there's only so much of it left.

Maybe if you miss the noise you could just make 'vroom vroom' noises yourself whilst driving? Or perhaps record some kind of soundtrack at a vintage car rally?

Fuel consumption? It don't grow on trees, there's only so much of it left.

Enjoy it while it lasts then*.....

*To purely wind up the eco-conscious.

I'm out now, time to go back to work.

The petrol and diesel are unlikely to have the same gearbox....gear ratios suited to diesel would be rubbish in a petrol & vice versa....

You're probably right, though still felt like you were having to short shift and change gear every 2 seconds to keep the diesel up to speed.

It don't grow on trees…

[s]All the more reason… [/s] sod it - beaten to it.

squirrelking - Member

Sbob, you're taking the whole STW-dick thing to new levels.

No, telling me what I want and being wrong about it is being a dick.

If you want peak power delivery in a very tight rev range then go ahead

Plenty of power between 4,500 and 9,000rpm in my old Honda, does that sound tight to you?

As for the Grandad statement I wasn't slating Hondas, I was merely using them as a very good example of engines that require a lot of work to keep them at their peak power

Rubbish, you used the term "over use" and preceded the name Honda with "just". Not that it bothers me that you were "slating" Honda, merely that you then lie about it.

If you like low down torque and avoiding changing gear then good for you, I'm happy for you.
Don't tell me what I like however, because it is clear you are talking out of your bottom, and it hits a nerve.

Much like my joking pensioner comments, eh pops?
Am I right? 😉

Diesel's don't have the same gear ratios. In my car, at 70mph it does about 2krpm, my dad's petrol is about 2.8krpm. In both cases roughly half way through the rev range.

However my diesel comes on really stronly at about 1.2krpm, and in his case it does basically nothing until.. well.. 4k or so! His is a 1.6 Focus - it's smaller, slower and less economical.

Still struggling to see how his petrol is better to drive.

Of course, a big V8 petrol would be much better, but that's a premium engine and has costs to match - not a fair comparison with a 2.0 TDI.

So, right

If you were looking to buy a mid-ranged car for around £10k, around 5 years old 2010 - 2011, and reckon you'll keep the car for 5 years ish.

Is it wise to look for petrols, or is diesel still okay?

FWIW, I was looking at a 2.0 VW Scriocco GT. Diesel.

If you are buying used, you can choose your fuel and then adjust the age or mileage to suit your budget. So it depends on

a) preference
b) mileage vs fuel budget/desire to rape the planet
c) short/long trip ratio.

"You're probably right, though still felt like you were having to short shift and change gear every 2 seconds to keep the diesel up to speed."

what diesel was that ? sounds broken.

Sbob, if you don't understand the nuances of the English language I don't think you should be wading into a technical discussion. When I said "you want" I didn't literally mean YOU nor was I dictating a preference.

Not sure what I'm lying about either, I explained my reasoning for picking Honda (very familiar and involved with other owners), I may well have chosen something else but can't think of something that would have illustrated my point in the same way. Again, if you have difficulty grasping the English language I would get some remedial lessons before making a cock of yourself again.

Whatever your actual point was there were plenty of ways you could have said it civilly. That you chose to be a dick about it instead of being reasonable speaks volumes about you as a person. If you have nothing useful to add then please do yourself a favour and don't waste your time replying.

what diesel was that ? sounds broken.

Octavia VRS, both mapped and standard. In fact the mapped cars managed to feel worse as they got through what few revs they had even quicker. Pretty sure they weren't all broken but felt that way in direct comparison to the petrol equivalent.

I do think diesels have their place and can be great cars, just not in that car. 330d/335d for example felt a far better all round package.*

*added as I'm not anti diesel cars in general

Octavia VRS, both mapped and standard.

What year? Older PD engines before.. er.. 2004-5 ish had mechanical PD injectors and they were definitely narrow power banded.

However they were still fast enough, if you knew how to drive them. And the huge torque in that narrow band was actually brilliant for driving on windy roads. My Ibiza felt far far quicker than my dad's Fiesta (and was far more fun to drive) despite the same bhp.

oh i agree - why would you want a diesel performance car.

recipe is something like take 1 x 2 litre engine bolt on big turbo.

result is not very nice to drive.

And the next person who posts up dyno graphs of engine speed vs power or torque gets a dirty look.

Dammit!

Of course, a big V8 petrol would be much better, but that's a premium engine and has costs to match - not a fair comparison with a 2.0 TDI.

How about a 2.0TDI and a 2.0T petrol?

Compare a Golf GTD to a Golf GTI
The diesel has more torque than the petrol but never gets near it in terms of performance

2 reasons:
Firstly torque is meaningless without considering gear ratios the petrol driver is effectively 1-2 gears lower than the diesel driver.

Secondly power is everything!

oh i agree - why would you want a diesel performance car.

Depends on the car. Lotus Elise - no. Audi A5 3.0 V6 TDI yes. BMW 535d - yes.

More than one way to enjoy driving.

How about a 2.0TDI and a 2.0T petrol?

Compare a Golf GTD to a Golf GTI

Well getting like for like depends on what you compare. Comparing similar displacement doesn't make as much sense as you'd think, because the engines work differently.

Comparing the GTI and GTD makes more sense though overall. Both essentialy the same type of car, and they have different pros and cons. GTI is for those who want the most speed, GTD for those who want plenty of speed but still economy.

A good comparison I'd say is bhp. I've compared a 105bhp diesel with a 105bhp NA petrol and there is absolutely no way in which such a small petrol is better.

With say a 150bhp turbo diesel and turbo petrol it's closer - but the diesel gets far better economy.

And comparing like for like on economy - a diesel will be vastly better.

molgrips

A good comparison I'd say is bhp. I've compared a 105bhp diesel with a 105bhp NA petrol and there is absolutely no way in which such a small petrol is better.

Is that a 105bhp tdi vs a 105na petrol? How did the torque figures compare?

Audi A5 3.0 V6 TDI yes. BMW 535d

Cruisers.

like comparing a harley to a gsxr imo.

Gimmie the audi or the beemer any day for a day to day car - but id rather the 2.0d in either ill be honest.

Depends on the car. Lotus Elise - no. Audi A5 3.0 V6 TDI yes. BMW 535d - yes.

There's a guy who lives near me with a brand new Audi TT...in diesel flavour...for the weekend. He drives a petrol golf to work!

I can't get my head round spending £30k+ on a sporty(ish) car like the TT and then try to save a few quid on fuel? Maybe he just really likes how the torque makes the road come alive?

I can't get my head round spending £30k+ on a sporty(ish) car like the TT and then try to save a few quid on fuel?

Environmental conscience?

Anyway it's not just a few quid, is it? It could be a couple of thousand quid over say 200k miles ( not done sums) and that pays for the stero upgrade, a DSG, the built in satnav or some other expensive options.

Woah there SK!
Maybe the light-heartedness of my initial reply was too subtle for you to understand, hence why you waded in with the insults. 💡

Maybe you should take my car for a spin; it always brings a smile with its cheeky looks and flower graphics. 8)

Environmental conscience?

Anyway it's not just a few quid, is it? It could be a couple of thousand quid over say 200k miles ( not done sums) and that pays for the stero upgrade, a DSG, the built in satnav or some other expensive options.

Since when was having a second, sports car with a diesel engine, environmentally friendly? 🙂

Also, what are the chances that he'll be sticking 200k miles (ie almost the distance to the moon) on a weekend car?

(it would take him 20 years of sticking 200 miles on it every weekend to hit that figure!)

My car always gives me a smile when I return to it in failing light after a long cold wet ride in the mountains... 🙂

Ah I didn't see the 'weekend' part.

Still - why not ask him? Perhaps he preferred the drive? Perhaps his weekends involve driving to Edinburgh or something?

A good comparison I'd say is bhp. I've compared a 105bhp diesel with a 105bhp NA petrol and there is absolutely no way in which such a small petrol is better.

I agree, but that's also argument of forced induction versus NA.

How about the 1.8TSI in the new Leon FR (180bhp) versus the Golf GTD (184bhp)

The Leon is giving away a huge amount of torque (250Nm versus 380nm) and yet the acceleration of the two cars is very similar (shorter gears and a bigger rev range make up for the comparitive lack of torque)

Now try finding a small diesel that compares well to the 1.0L Ford Ecoboost

How about the 1.8TSI in the new Leon FR (180bhp) versus the Golf GTD (184bhp)

It'd be an interesting comparison. Probably come down to preference and what you want out of it.

Now try finding a small diesel that compares well to the 1.0L Ford Ecoboost

It'd be a 1.6 bluemotion type thing. They are quite driveable by all accounts.

Ah, sod it. I'm back in (bored at work)

Depends on the car. Lotus Elise - no. Audi A5 3.0 V6 TDI yes. BMW 535d - yes.

But a petrol version is even better - the 535 is at least accompanied by a sonorous soundtrack. The BMW X35's a very fast and very competent, but to me offer very little else.

Now, going off topic a bit...

With regards to cars doing 200k, I can't see many modern cars getting that far without serious money thrown at them at some point - BMW's seem faiurly prone to eating turbos plus HPF issues that are pricey. There are a fair few guys at work who have had Passat's etc needing turbo replacements by 70k. The 7 speed DSG box isn't known to be the most reliable thing.

The drive for ever greater ecomony and lower emissions does seem to be leaving us with cars that will throw up some big bills early on. I have a friend who had a 540 that went on to 275k befoure rust killed it with very little money having to be spent on it, but that was a massively understressed, lazt engine.

I've had all sorts of petrol and diesel cars. I have a dinosaur of a 3.2 V6 in my Golf at the moment, which does 25mpg overall and cracks 35 if I drive like Miss Daisy.

That's almost the same on fuel as the supposedly more fuel efficient 2.0T lump I had in my old S3. Big NA is also the most smooth and luxuriant driving experience I've come across. The R32 will even accelerate reasonably at just idle speeds (i.e. not using throttle), which is something I've previously only been able to do with diesels.

But the main thing I want to add to this is...

Depreciation!

I only do around 8-9k miles per year; and only 5k of those are not on business. Fuel and VED costs do need to be considered, but - depending on what your budget is and what you buy - depreciation is a much larger cost in my experience.

My 2p:

Firstly I like the way diesels drive, some of my mates won't touch the dark stuff - "it's horrible to drive" and sure enough they drive them like a petrol - they floor it straight through the power band, onto the redline next gear barely sees the powerband at all - lots of noise, revs, soot, very little forward motion and 20mpg. Drive like a diesel though and they do that whole 'inoffensive pace' thing really well - they're also not slow - real world stuff like 30-60 joining a motorway they're faster than the equivalent petrol and more relaxing to drive unless you're city driving IMO.

After 10 years of diesels I find most petrol cars harsh and gutless.

In regards to costs - there is some formula that was dreamt up by some petrol head (on Pistonheads I think) who said that you need to do 25-30k miles a year to make it work - I don't see how Diesel is 6% more expensive than Petrol - even the latest tiny turbo petrol engines aren't anywhere near that close to diesel - certainly not 'in the real world' truth is, even the famous 3 pot Ecoboost isn't great on fuel unless you nurse it everywhere - and sorry, the diesel denyers can point to supposed reliability issues with diesels - but the technology they use the make them more flexible which supposedly fails expensively all the time is the very same technology they're using to make a tiny petrol efficient.

No to me it's the same formula as it's always been short trips or lots of stop-start driving - petrol, longer trips diesel.

I only do around 8-9k miles per year; and only 5k of those are not on business. Fuel and VED costs do need to be considered, but - depending on what your budget is and what you buy - depreciation is a much larger cost in my experience.

And works in your favour when buying a car second hand, especially in this country where people are obsessed with fuel ecomony and Co2.

In regards to costs - there is some formula that was dreamt up by some petrol head (on Pistonheads I think) who said that you need to do 25-30k miles a year to make it work - I don't see how Diesel is 6% more expensive than Petrol

I think that forumla is taking into account the likes of purchase price plus servicing. In some cases the latter is more expensive on dervs than petrols - local BM indy charges more to service a 330d than a 330 petrol.

even the famous 3 pot Ecoboost isn't great on fuel unless you nurse it everywhere

In my experience, Ford's economy claims are even greater works of fiction than those of other manufacturers. Even driving like miss daisy on lots of long motorway trips (suited to diesels) mine is way off the claimed.

If I apply the same reduction on ecomomy to the petrols that I am looking at, then it won't cost me any more to fuel and the BIK is lower and a lower list price. Stacks up for me.

if I drive like Miss Daisy.

Miss Daisy does not drive, she has a chauffeur.

I think that forumla is taking into account the likes of purchase price plus servicing.

Yes, it assumes buying from new where you pay more. Second hand you (can) pick the price point and choose the age, so diesel need not cost more to buy.

local BM indy charges more to service a 330d than a 330 petrol.

I wonder why? The expensive items in a diesel aren't service items.

oil and oil filter/fuel filter are more expensive on most turbo diesels.

but not a huge amount.

the void between the cost of a used petrol vs used diesel is what makes the biggest difference for me and could drive me back into a petrol.

i honestly dont know what ill buy once my 1.9 8v diesels bite the dust - get taxed off the planet.

i honestly dont know what ill buy once my 1.9 8v diesels bite the dust

Another diesel? Modern ones aren't the disasters you appear to think.

About 10 years ago I bought a Ford Focus. I sat down and worked out, doing an average of 12k a year mainly on motorways and A roads, how much a petrol and a diesel would cost to run.

Factoring in tax, fuel cost difference, service intervals (which to be fair is now not so important as more modern diesels are looking at 10k gaps) and every other expense I could think of, I did my sums.

Over a year the difference was something daft like £10.

I went for the petrol because it was more fun to drive.

they are at the age i buy em......

(which to be fair is now not so important as more modern diesels are looking at 10k gaps)

When did diesels have shorter service intervals?

I'm on variable intervals, I get about 17k between lights.

We have a '95 Mazda Bongo with a Ford/Mazda 2.5 diesel turbo lump (same as the Ford Ranger) - recommended 4k service intervals.

The mk1 diesel Focuses (Foci?) I was looking at had an interval of about 6k, compared to an 8/10k petrol interval, and petrol services and spares were cheaper.

I'm potentially picking up a new-ish 2009 Octavia diesel this week - service interval is 10k.

That's my basis for comparison. 🙂

trail_rat - Member

they are at the age i buy em......

Post of the thread! 😆

My diesel doesn't seem massively more expensive to service than my previous petrol. I think the oil is a bit more expensive - PD oil and more of it, than the engine in the petrol Fiesta that went before it.

My current car supposedly requires services every 10k miles, but I've stretched it out to 15k miles as 99% of my miles are sat at a steady speed on A roads and it's a decent size, unstressed engine in a small car. I've done that for over 100k miles now and it doesn't seem to have suffered any ill effects.

My Wife's previous Peugeot 308 1.6 was a god awful car, but had a 20k mile service interval which impressed me (about the only thing that did about that car).

Anyway, have we come to a conclusion yet?
Just to stick my oar in - for the mileage the OP is considering it would be diesel for me all the way. I wouldn't want to be covering those miles in a high revving, fizzy petrol engine. Fine for a weekend car or lower mileage.....but diesel would cover those miles in a more relaxed fashion - I find cars that are buzzing away at 3k+rpm on the motorway very tiring.

When did diesels have shorter service intervals?

I'm on variable intervals, I get about 17k between lights.

They all seem the same these days - apart from Ford who still seem to use short service intervals. My Ford is in every 12k but my MINI's and BM's in the past have been up to around 18k (depedning on how they were driven). Only VAG seem to offer standard (10k or 1 year) or the long life.

Just to stick my oar in - for the mileage the OP is considering it would be diesel for me all the way. I wouldn't want to be covering those miles in a high revving, fizzy petrol engine. Fine for a weekend car or lower mileage.....but diesel would cover those miles in a more relaxed fashion - I find cars that are buzzing away at 3k+rpm on the motorway very tiring.

But I'm often surpised how bad NVH levels can be in diesels at motorway speeds - my Grandad has just bought a new Passat and I thought it was quite gruff at motorway speeds. That may be down to the fact that it's one of the smaller, lower powered versions.

It's not just petrol cars that are going down in capacity - a 1.6 seems pretty diddy for a car like a Passat.

I wouldn't want to be covering those miles in a high revving, fizzy petrol engine. Fine for a weekend car or lower mileage.....but diesel would cover those miles in a more relaxed fashion - I find cars that are buzzing away at 3k+rpm on the motorway very tiring.

My petrol revs to 8k and sits at 1,800 at 70mph. Hardly fizzing away and not a big engine.

But I'm often surpised how bad NVH levels can be in diesels at motorway speeds

Funny. My Passat (older 2.0 TDI) is very noisy at low speed but very quiet on motorway. And my dad's car is almost silent at low speeds but because it's near 3krpm on the motorway it's actually a lot noisier.

a 1.6 seems pretty diddy for a car like a Passat.

A diesel gets it's power from more air and more fuel. But because it's compresison ignition you can simply ram more pressurised air into the cylinder without worrying too much. So a bigger turbo and smaller cylinders is the same (actually slightly better due to higher pressure and there being more air molecules closer to the fuel droplets) as smaller turbo and bigger cylinder. Same amount of air, same amount of fuel = same power. Well.. up to a point.

peterfile - Member

My petrol revs to 8k and sits at 1,800 at 70mph. Hardly fizzing away and not a big engine.

What's that then? I've never been in a petrol that revs that low at 70mph.

Most petrols I've ever been in sit at around 3k rpm at 70. My Wife's 308 was even higher; about 3.5krpm and a mates Corolla T-Sport which had about 190bhp say at around 3.5-4k rpm I seem to remember.
My Ibiza is at around 1800rpm at 70 - 1.9 TDi with 130bhp.

stumpy, my mistake...I was reading figures for the auto.

I checked mine this morning and it's 2,000 rpm at 70mph (so not too far off though!), and engine noise is barely perceptible at that speed unless accelerating.

It's the B8 2.0 TFSI engine, which seems to be highly rated (although I know nothing about engines other than info I can find online!).

My brim to brim for that last 500 mile trip worked out at 39.5 mpg, that's with winter tyres on, not driving like an idiot, but no cruise.

What kind of driving peter? As said I'm interested in that engine for when I next change the Passat. In about 2025 🙂

Mol, my 16 mile commute is a few miles of residential and city driving, with the rest being motorway driving at 40-60 mph, generally in medium traffic. I get about 38-40 mpg.

Sitting at 75 on a long motorway journey will return about 40 mpg.

30 mins of congested city centre driving doesn't seem to dip below 26/27 mpg (on the DIS, but it isn't too far off my brim to brim calcs though).

What is most interesting (for me anyway) is that the mpg doesn't seem to take too much of a hit when you're on something a bit more twisty or are up and down the gears. Up the A82 for example...100 miles of a mixture of city, 30mph twisty stuff along the loch and then loads of quick and hilly A road with a few overtakes...making no attempt whatsoever to drive economically...I seem to get about 36mpg.

It seems pretty good for a car that will get to 60 in 6.5 seconds and has plenty of power for A road overtakes.

It also sounds quite nice for a relatively small engine.

The torque (that everyone who likes diesels bangs on about) is about the same as in the 2.0 diesel.

Still does not compare that well to the ease with which I can beat 50mpg for a tank though on my diesel. I can get 48 ish on twisties with no effort, and Around 60 with grey effort. On motorways I can easily beat 60 in the summertime. And that's in a pre-bluemotion car.

I would like to try one of these cars to see how well I can do.

Well aye, obviously a diesel engine of comparable size will beat a petrol in pure mpg terms.

But, as I mentioned earlier, the diesel version of my car was more expensive to buy and at 15,000 miles per year I'd only be saving £300-400 a year in fuel, so it would take me years to make the diesel cheaper.

I focus on the cost to me to run over the course of ownership, rather than per journey or per month etc. There wasn't anything in it overall between the two cars and I far preferred driving the petrol, it suited me better. It's nice to be able to take cost out of the equation and just choose your favourite.

It's the B8 2.0 TFSI engine, which seems to be highly rated (although I know nothing about engines other than info I can find online!).

They are good engines but let me know how you get on when you rev it to 8000rpm

I'm more concerned about environmental impact (but also cost*), and I'm thinking of petrol because diesel is dirty stuff and it also can cost more CO2 to produce although this isn't well known.

* having said that a diesel won't cost me more than a petrol - it'll just be older or higher mileage.

They are good engines but let me know how you get on when you rev it to 8000rpm

Why would he want to do that?

peterfile - Member

stumpy, my mistake...I was reading figures for the auto.

I checked mine this morning and it's 2,000 rpm at 70mph (so not too far off though!), and engine noise is barely perceptible at that speed unless accelerating.

It's the B8 2.0 TFSI engine, which seems to be highly rated (although I know nothing about engines other than info I can find online!).

Ah. Erm, the thread seemed to be going in the direction of comparing the economy of diesels against small three cylinder petrols like the 1 litre Ford Ecoboost (well, it was at the start of the thread 😀 ).
It was that kind of engine that I was basing my comments of 'high revving, fizzy petrol engine' on.....not a 2 litre, which I wouldn't call a small engine.

One of the reasons I got rid of my old car - ignoring the almost terminal rust - was the fact that I couldn't get any more than about 40mpg out of it.
At the time I was doing 100 miles/day commute, so swapping to a diesel that was vastly quicker and got me about 40% more mpg (from 40 up to 55mpg, easily) was a no brainer.
When I got the car, petrol and diesel was about the same cost (petrol might have been about 2p/litre more than diesel) and the petrol was costing me about £51/week in fuel compared to £37 in the diesel (quick calc assuming fuel was about £0.90/litre when I bought the car, which I think it was). So, a £14/week saving in fuel costs.

Unfortunately, a car for me has become pretty much an appliance rather than something to particularly enjoy.

molgrips - Member

[i]They are good engines but let me know how you get on when you rev it to 8000rpm[/i]

Why would he want to do that?

I imagine that comment came from this previous post....

peterfile - Member

My petrol revs to 8k and sits at 1,800 at 70mph. Hardly fizzing away and not a big engine.

Oh I see.

Stumpy, the context for quoting 8k was because you referred to "high revving, fizzy petrol engine".

I don't really know what my car will rev to (and I'm unlikely to find out), but the dash shows a number 8 as the high point, so I figured that was a good guess.

[img] [/img]

No way that'll rev to 8k anymore than it'll do 180mph.

You'll get to 7000, maybe 7200 before the limiter comes it, by which you'll be well out of the power band anyway.

18 months now with the Lodgy TCE. The fuel used is the same on the trip computer and filling station pumps but the trip distance over reads by about 3%. 5,8l/100km average over that time (so a real 6l/100) with a mix of town and mountain roads. I generally get better than 5.5l/100, Madame uses a little more and since junior has started driving the consumption has reached 6.

As Molgrips states the CO2 figures for diesel are misleading as they only include CO2 at the point of burning rather than the overall carbon footprint. There is also the supply and demand balance to consider; there is not enough demand for petrol in Europe so refiners export to distant land such as India and the US. Sending coals to Newcastle because there are too many diesel cars in Europe and not enough petrol ones. The tax system and the way CO2 emissions are calculated both need a rethink if the price you pay for fuel is to reflect the overall impact environmental of burning it. IMO diesel is too cheap.

You'll get to 7000, maybe 7200 before the limiter comes it, by which you'll be well out of the power band anyway.

I knew there was an electronic limit on the speed, didn't realise there was also one on the rpm. Maybe I'll try and find it on first gear coming out of the car park tonight 🙂

Also servicing on my 2.0CR Tdi seat is exactly the same cost as it is on the 2.0TFSI version which is a cheek really - those spark plugs can't be cheap.

They cost the same to buy new +/- 5% but that has more to do with the spec.

The Petrol ones are cheaper second-hand, but according to the dealer it's because no one wants a 25mpg saloon or estate now unless it's very sporty.

So I still can't see why you need to do so many miles to save any money.

peterfile - Member

You'll get to 7000, maybe 7200 before the limiter comes it, by which you'll be well out of the power band anyway.

I knew there was an electronic limit on the speed, didn't realise there was also one on the rpm. Maybe I'll try and find it on first gear coming out of the car park tonight

Most cars since the early 80's have had some sort of rev limiter - mostly to stop you making the engine explode - something to do with 'overlapping' or something - anyway, even without it at some point or other they simply can't keep the air / fuel coming in fast enough to rev any higher and they stop naturally.

The Petrol ones are cheaper second-hand, but according to the dealer it's because no one wants a 25mpg saloon or estate now unless it's very sporty.

So I still can't see why you need to do so many miles to save any money.

My car does about 10mpg less (over a tank) than the equivalent diesel and was £1,200 cheaper to buy (at 3 years old).

25mpg? I can barely get to that driving about town.

I have the same engine in my car. 6700rpm is the limit. The red bit on the rev counter is just decoration

It doesn't bounce of the limiter like something like a Civic Type R would. It just sits there not revving any further. Pointless to take it passed 6000 rpm anyway, peak torque is around 2000 and peak power from 4300-6000rpm.

Not sure it needs a speed limiter though (other than drag squaring with speed that is)

I bought a Skoda Fabia estate new two years ago. its a 1.6 diesel 105bhp.

I chose the diesel over the petrol, but in hindsight I would choose the petrol version now.

The only factor governing my choice was I prefer the diesel torque. Financially ( for me) its not worth it.

richmtb

Not sure it needs a speed limiter though (other than drag squaring with speed that is)

Tyres probably.

Valve bounce (the valve spring not strong enough to keep the valve following the cam) and hydraulic pump up (on cars with hydraulic valve followers) used to be what limited how high engines would rev without a limiter.

When "tuning" engines one usually uses stronger valve springs and suitable followers to raise the rev limit. Even with lots of lightening, balancing and stress relief the higher rev limit soon uses up the fatigue life of other engine components such as the valves, pistons, rods and crank. My competition engines were base on stock engines with a red line at just over 6000rpm. They would run for years at that speed but using 7000rpm needed a rebuild each season (if they lasted that long). Engine life at 7500rpm was a few minutes and it was only ever worth risking if backing off the throttle was going to result in going off the road. I never used a rev limiter and 7000rpm was as familiar to my ears as the e-string of my guitar.

Valve bounce (the valve spring not strong enough to keep the valve following the cam) and hydraulic pump up (on cars with hydraulic valve followers) used to be what limited how high engines would rev without a limiter.

On a conventional road engine piston speed becomes is as much of a limiting factor as valve bounce. Honda VTEC's typically had redlines above 7500 rpm with conventional valves

You need a short stroke engine to lower piston speed (like a motorbike) or a short stroke engine and pnuematic valves (like an F1 car) to get serious RPM

peterfile - Member

The Petrol ones are cheaper second-hand, but according to the dealer it's because no one wants a 25mpg saloon or estate now unless it's very sporty.

So I still can't see why you need to do so many miles to save any money.

My car does about 10mpg less (over a tank) than the equivalent diesel and was £1,200 cheaper to buy (at 3 years old).

25mpg? I can barely get to that driving about town.

What are you getting? it's a 2.0 turbo A4 no?

I'm getting 50mpg (when roofrackless) from my Seat Exeo - I only spotted one Petrol version when I was looking which had the same engine as your A4 - I was told 25mpg was the norm for 'mixed driving' - my Exeo will get about 40 doing the same.

What are you getting? it's a 2.0 turbo A4 no?

I'm getting 50mpg (when roofrackless) from my Seat Exeo - I only spotted one Petrol version when I was looking which had the same engine as your A4 - I was told 25mpg was the norm for 'mixed driving' - my Exeo will get about 40 doing the same.

My mates 300bhp V6 [i]S4[/i] Avant has an average of 25mpg.

Mine is the A4 B8 2.0 TFSI in manual flavour. It seems to be an pretty economical engine considering the moderate power.

(Honest John's real mpg and forum searches reveal that 35mpg is overall average for most, with most hitting high 30's/40 on a run.)

In the 2,000 miles since I bought the car I've been keeping brim to brim calcs and have hit 35mpg (but I've had a few more longer journeys in there over xmas period so will probably dip a bit now I'm back at work)

From my earlier post...

Mol, my 16 mile commute is a few miles of residential and city driving, with the rest being motorway driving at 40-60 mph, generally in medium traffic. I get about 38-40 mpg.

Sitting at 75 on a long motorway journey will return about 40 mpg.

30 mins of congested city centre driving doesn't seem to dip below 26/27 mpg (on the DIS, but it isn't too far off my brim to brim calcs though).

What is most interesting (for me anyway) is that the mpg doesn't seem to take too much of a hit when you're on something a bit more twisty or are up and down the gears. Up the A82 for example...100 miles of a mixture of city, 30mph twisty stuff along the loch and then loads of quick and hilly A road with a few overtakes...making no attempt whatsoever to drive economically...I seem to get about 36mpg.

Honda VTEC's typically had redlines above 7500 rpm with conventional valves

As I understand it, the reason these can rev higher is that the valve timing switches to more valve overlap which is less efficient in normal driving, but at high revs when there's a lot of air flowing through it allows more air to flow more smoothly. Jolly clever.

Clever and now quite common, even the Dacia has variable valve timing as do all the Renaults and Merecedes that use the same engine.

Yeah Toyotas do, however they don't seem to do it the same as Honda, they don't rev to 8krpm.

EDIT from wiki:

"[Honda's VTEC] is distinctly different from standard VVT (variable valve timing) which advances the valve timing only and does not change the camshaft profile or valve lift in any way."

So VTEC has two different sets of cams, whereas VVT only adjusts the position of the camshaft itself.

@peterfile that's better than I expected, if the BIK isn't too murderous I'd consider petrol next time - although I've got my eye on a 3.0Tdi Quattro.

Your mate with an S4 is doing well, mate of mine has got a B7 RS4, it might have got better now it's not so new to him, but I know it was in the low teens for a long time ha ha.

P-Jay, I think the older V8 S4s were horrific on fuel (he had one too), but the B8 S4 is significantly more frugal (with two fewer cylinders too I suppose).

I've never driven his car, but it seems to me to be a great compromise between practicality, cost and sporting ability. His running costs are much, much smaller than an RS4...but still high enough to put me off for now. I very nearly bought an S4 Avant (mrs PF works for Audi), but just couldn't get the numbers to add up over 3/4 years.

Yep very clever, especially given how long ago they developed the system.

There are other cleverer systems though. BMW valvetronic allows constant variation of the intake valves lift.

Lexus have a V8 that can switch between Atkinson and Otto cycles depending on engine speed

If you fancy properly geeking out on the subject there is a good description of various VVT schemes [url= http://www.autozine.org/technical_school/engine/vvt_5.html ]here[/url]

There are other cleverer systems though.

Fiat multiair

Lexus have a V8 that can switch between Atkinson and Otto cycles depending on engine speed

Damn, another idea I came up with stolen by a manufacturer...

Koenigsegg trumps all - no camshaft to get in the way. Been working for years on marine diesels and I'd imagine it would scale down very easily with direct injection and hydraulic/electronic operated valves.

Choose profile, point, shoot.