[Closed] Diesel vs petrol road cars

Test drive them back to back.

I'd love to but that might be challenging, I think my local Ford has like one tester (potentially the 177PS hybrid 😯 ).

What sort of driving? I'd say this;

Regular long distance - Diesel.
Regular short distance, and/or stop/start - Petrol.

Where do you do most of your miles!?

Motorway or town!? Diesels are best on the Mway as I'm sure you're aware. Less people around to breathe the nasties they emit too.

Diesels are significantly dirtier - you trade MPG for NO2
We just swapped Mrs J's diesel for a petrol to reduce our NO2 contribution
Depends on the type of driving you'll be doing.
There is also a suggestion that the tax on diesels may increase significantly.
I'll be swapping my diesel for a petrol or hybrid when it's due for changing.

http://www.bbc.co.uk/news/business-33254803

Lower emissions on the diesel.

I'd be hard pressed to say. When I do motorway miles it tends to be long distances; I might not touch a motorway for a month, then have to do a 500 mile round trip.

Lower emissions on the diesel.

Do you really believe that, Diesels especially as they age chuck all sorts of obnoxious stuff out of the back, it's very much on the agenda to ban them from major cities the Paris mayor has a real thing about it. The diesel emissions benefit is a bluff / smoke (litteraly) and mirrors IMO

Anyway unless you are doing high milages the petrol all the way imo.

You are quite right to note service intervals, look at costs too. More expensive maint required on diesels. Higher purchase price ?

We have an obsession with diesel cars in Europe partly as on the continent the fuel is cheaper vs petrol. In Asia, US etc you hardly see them in private cars.

Going new I'd look hard at a petrol option.

Fwiw I test drove a 2012 Mondeo with the 1.6 ecoboost before I bought my current car. Lovely engine and could propel the estate lightly loaded pretty easily.

The 170ps diesel versions I drove were quicker for a lazy driving style (ie keeping the revs down but nipping along inside the limits).

I ended up with a Passat. There I found a late 150 ps 1.8t and similar experience vs the 170ps tdi I ended up buying.

Buying secondhand there was sod all choice of petrol ones of both cars (both ones I tried were manual but changed my mind and went for an auto) so I ended up with an oil burner.

Economically for me I think diesel works 20000 a year of mixed driving with plenty of long motorway runs but I'd have had petrol for choice.

It won't matter two hoots if it's on PCP. Pick whichever one gives you the best deal, because in 3 years time you'll chop it in against a new one.

^^ I've had one diesel (2.7tdi auto) in the days we where doing 20k pa plus of mostly motorway driving.

Interested in this. Diesels for the last 10 years but thinking of going back. I do about 16k a year. Lots of motorway, but lots of stop start too. Particulates etc are a real thing. And it seems kind of hard to trust anyone's environment data at the moment...

Diesels are not 'best on the motorway'. Big engines and cars with auto boxes are.

In my view it comes down to your overall mileage a year, and if you do a lot of short journeys. Properly calculate the running cost over a year, taking into account servicing, fuel, and crucially for a new car, road tax.

I've just done the same, and for my 15k per year, despite it all being long motorway journeys, have opted for petrol having had run diesel for the last ten years. The difference in running cost over a year is around £500 for me, and I'm happy to pay that for the extra refinement of a big petrol engine. On the car I've ordered there is no difference in price between the petrol and diesel versions, and the dealer was happy to arrange back to back tests for me.

I also suspect that diesel cars are going to start getting hammered on road tax, and on fuel tax as well.

Diesels are much more dirty than petrols and kill lots of small children

If the brochure book is to be believed, the diesel has considerably better MPG

It will be. They over-estimate petrol more than diesel, if anything.

There are websites that give 'real world' mpg stats for cars, but they are of questionable benefit, since I seem to far exceed their averages.

I will be tempted to try turbo petrol next time, because of environmental factors, but I will need to demonstrate that *I* can get 50mpg or so on long trips.

I don't see why diesels will have higher service costs though - provided you look after your DPF.

I don't have enough data but seems that fuel consumption our diesel car less affected by bikes on a roof than petrol car. Again, I should check this properly before claiming anything.

Do you really believe that

In the absence of any other information beyond your ephemeral "all sorts of stuff," I can only take it at face value.

There are websites that give 'real world' mpg stats for cars,

That's a good idea, I'll have a look.

but they are of questionable benefit, since I seem to far exceed their averages.

This doesn't surprise me. (-:

Properly calculate the running cost over a year, taking into account servicing, fuel

... insurance. That's going to be tricky but I'll have a go.

crucially for a new car, road tax.

Seems that as long as I keep it under 120g/km, it's £30pa. It jumps up quite alarmingly after that. 2.0 diesel is listed as 115, 1.5 petrol comes in at 134. So that's 400 quid over 4 years.

Thanks all.

Last time we changed cars, 20k was the break point for fuel choice, this was when the wifes commute was a daily 100 mile round trip.
Massive mileage drop now means a not very economical, but cheap in every other way, petrol car. More economical petrols were available, but the current one is amusing.
We are buying used though, so our running costs may be different to pcp/lease/finance deals depending what is included.

I prefer the lazy slow revving torquey driving style of a diesel.

Do the test drive in the hybrid. Then buy the petrol.

If you were planning on buying it and keeping it forever I would say petrol, however on a PCP you won't have enough time to run into the problems a modern diesel car can have and it's under warranty anyway.

In which case just do the sums on which will cost you least in petrol and tax and get that one.

Any particular reason for PCP? I'd look at all the finance options. When I did so recently, PCH i.e. a personal lease was by far the most cost-effective way to get in to a new car.

Look carefully at the figures on PCP, if there are big contributions and v. low interest rates then great. Otherwise, they don't tend be as good as they used to be - largely due to the way residuals are calculated.

As discussed, petrol v diesel is about intended use and don't get hung up on the CO2 figure as the only measure of emissions.

Modern small capacity turbo petrol engines are really great. The 1.4 125ps in my Golf delivers a real 50 mpg at 70 mph and I have a combined economy of 37 mpg over the first 2000 miles. This is a mix of short journeys on rural B roads and dual carriageway/motorway use. Small fuel tank means limited range (400 miles) but it is quiet, smooth and generally pleasant (dull) to drive. It in no way feels underpowered on the motorway. Yes, it has much less power/torque than my old 320d but it is still sufficient. Also note, that the Golf is actually more economical in that mixed driving than the BMW was. Plus the BMW was hateful to drive in stop/start traffic (see point about intended driving for merits of petrol v diesel).

Buy the hybrid?

I prefer the lazy slow revving torquey driving style of a diesel.

Turbo petrols have that too.

Modern small capacity turbo petrol engines are really great. The 1.4 125ps in my Golf delivers a real 50 mpg at 70 mph and I have a combined economy of 37 mpg over the first 2000 miles.

Still worse than diesel though. My old Passat is bigger, heavier, more powerful, is auto and gets 60mpg at 70 and about 46 or more on B roads.

Lower emissions on the diesel.

Still worse than diesel though. My old Passat is bigger, heavier, more powerful, is auto and gets 60mpg at 70 and about 46 or more on B roads.

The 'cost' of diesel v petrol when buying new is about more than MPG. You must factor in the cost at purchase, VED, fuel cost, servicing and residuals. For everyone, there is a point where diesel does become more economical.

The point I was attempting to illustrate is that the gap between petrol and diesel has narrowed significantly and aside from the pure financial cost, there is an intrinsic value to each in terms of how they drive.

I simply prefer driving a petrol car but others prefer diesel. This, less quantifiable value, should also be considered.

The 'cost' of diesel v petrol when buying new is about more than MPG. You must factor in the cost at purchase, VED, fuel cost, servicing and residuals.

You don't need to factor in residuals. Depends on how you price it up. If you intend to keep a car as long as you can it's not an issue.

The point I was attempting to illustrate is that the gap between petrol and diesel has narrowed significantly

I agree with that. Both in economy and driveability.

Any particular reason for PCP? I'd look at all the finance options. When I did so recently, PCH i.e. a personal lease was by far the most cost-effective way to get in to a new car.

Because a) I don't have a deposit and b) if I get a personal lease and then lose my job I'm stuffed (AIUI).

I went petrol on my latest car after twenty years of diesel cars for various reasons (nasty particulates, over complicated expensive to repair engines, etc etc,) but one of the nicest things is I don't have to go near the horrible smelly shite when I fill up anymore..
Diesels are on the way out imo,

This might be interesting:

http://www.honestjohn.co.uk/realmpg/volkswagen/passat-b7-2011

1.6 TDI is not far off 50% more economical than the 1.4 TSI, which I would say are comparable engines.

Do you have a fuel card or can you claim business mileage at HMRC advisory rates?

Business mileage for a fuel efficient petrol/hybrid is a nice little earner.

Because a) I don't have a deposit and b) if I get a personal lease and then lose my job I'm stuffed (AIUI).

Understood. However, just be clear how you are exposed in a PCP if you haven't made a large initial payment and you do need to end the contract early. In this scenario, you could have negative equity and have to pay to hand back the car.

With a lease, you can get contracts with small upfront payments. If you have a short lease and keep the spec sensible/jump on a good deal it can work out very cheap indeed over the term.

There is a balance of risk versus outlay. Also, depending on your allowance, there could be potential to keep the monthly below the annual allowance so you can put aside cash 'just in case'.

Went back to a petrol estate after a couple of diesel estates. Don't do enough mileage and most of it is local short trips and stop/start driving, so wanted to avoid the DPF problems

Auto box, petrol engine and big heavy car means low mpg, but that's fine as on the whole we don't do a lot of mileage

I was looking at cars 4-7 years old, generally at the premium estate end of the market. Trying to find a petrol was very difficult, loads of diesels around but not many petrols

Do you have a fuel card or can you claim business mileage at HMRC advisory rates?

I currently have a fuel card, and then then am billed retroactively for personal mileage. I [i]think[/i] this will change when the car goes back though.

Business mileage for a fuel efficient petrol/hybrid is a nice little earner.

Thing is, I don't do a vast amount of business miles these days (in fact, I've just checked and I've not done any at all for over 12 months). It's a hangover from when I was in a different role, it's really just a perk now.

It's going to be interesting when the time comes to buy a new/newish car as I am okd school and see all fhese small (1.4-1.6) petrol turbos as whinny little undsr torqued motors. Did test drive the new Golf when it came out but very sceptical. It may be a search to find a 2l non turbo petrol in a small/medium car. Interesting Golf 1.4 comments above, they do match our test drive.

Roadtax - complicated and can change. When I bought my car in 2007 it had normal road tax, now its £500. Who is to say there won't be a diesel backlash ?

Cougar I hear you on empirical / pub talk but you only have to stand behind a diesel once its a few years old when you start it up or see them driving around a city. When the VW scandal broke many testing companies refused tv companies requests to retest cars on camera as they are afraid of an industry backlash, huge huge vested interests at work. Companies like VAG and French have invested billions in diesel tech.

Understood. However, just be clear how you are exposed in a PCP if you haven't made a large initial payment and you do need to end the contract early. In this scenario, you could have negative equity and have to pay to hand back the car.

With a lease, you can get contracts with small upfront payments. If you have a short lease and keep the spec sensible/jump on a good deal it can work out very cheap indeed over the term.

There is a balance of risk versus outlay. Also, depending on your allowance, there could be potential to keep the monthly below the annual allowance so you can put aside cash 'just in case'.

That's really useful, thanks.

I was looking at PCP because I believed it to be "safe" relative to a lease, though I'm not that fussed about a brand spanker. I went and spoke to a few garages at the weekend and put a few figures against it, and because their interest rates are different there's precious little difference between their new and used prices. I suppose I should've asked this question first!

"Putting some money aside" is something I was hoping to do, but is looking increasingly difficult. It's all quite stressful and annoying, I was told when the change was announced that I'd be better off, but either I'm doing something fundamentally wrong or that's a flat-out lie.

Diesels are not 'best on the motorway'. Big engines and cars with auto boxes are.

Why does an Auto box make any difference on the motorway? Unless there's very heavy traffic I never change gear on the motorway.

I agree Simon, auto boxes make no difference on the motorway, round town they're ace but on a motorway run no different from a manual IMO

In the absence of any other information beyond your ephemeral "all sorts of stuff," I can only take it at face value.

You'd have to be a bit of a bellend to buy a diesel just to see a few more quid in your pocket IMO.

I agree Simon, auto boxes make no difference on the motorway, round town they're ace but on a motorway run no different from a manual IMO

As said - traffic jams on the motorway are the worst place to have a manual.

For most folks, you're better off taking a cash allowance instead of a company car, as the company cars are often taxed quite hard.

So if you just want a car to pootle about in and are not fussed about a new car, then the cash allowance is just extra cash. You need to find a bit of money to buy a car up front, but that car is yours and you don't need to continually pay money towards a car every single month

If you do lots of miles or are hard on your cars then sometimes a company car works out better

In general, the move to cash allowances means most folks are better off long term, but maybe not in the transition period

I am okd school and see all fhese small (1.4-1.6) petrol turbos as whinny little undsr torqued motors.

By old skool you mean wrong?

1.6 TDI 110bhp max torque 250nm @ 1500rpm
1.4 TSI 125bhp max torque 200nm @ 1500rpm.

Not much in it. Interesting to note that the max torque of the petrol engine is at the same low engine speed as the diesel.

Diesels have always been filthy. Better on co2 emissions but filthy. That hasn't changed with the new tech engines. All the new tech is based around covering up the filth and making it invisible. Out of sight out of mind. In a city polluted by Diesel engines a modern petrol engine will be emitting air that is less toxic than the air it sucks in. Thousands of people a year are killed through pollution caused primarily by Diesel engines. That is a well established understanding.

yep, little petrol turbos are actually quite torqey.

Ford's 1.0 ecoboost delivers up to 200 Nm from 1400 rpm

That more torque than the 2.0 n/a in a Honda S2000!#

edit - mixing up my units, the 2.0 honda actually has 220 Nm, but still...

That hasn't changed with the new tech engines

Sure about that?

SCR actually gets rid of harmful NOx by turning it into water and nitrogen. A DPF catches the soot and then actually burns it up into CO2 in secondary combustion. It's not just moving it around.

I think you're wrong about the new tech.

Now that's not to say they are as clean as petrols, but the new tech is much better. There are however other issues with diesel production in the first place...

@molgrips, whinny and over-revving. Why don't motorbikes last 100,000 miles ? See the Golf owner review above. Customer choice. I won't be buying a small petrol turbo. Fuel injected 2 litre for me in mid sized car. Mrs B's Micra is 1600 non-turbo and our Yaris was 1.3. I won't buy a bigger heavier car (Golf/A3 size) with a turbo version of those engines.

SCR actually gets rid of harmful NOx by turning it into water and nitrogen. A DPF catches the soot and then actually burns it up into CO2 in secondary combustion. It's not just moving it around.

Ah, but the catch is you need to be doing the right kind of driving for the DPF to do its job properly. Fine if as well as town driving you do longer motorway runs but probably best avoided if you don't as you risk a clogged DPF and expensive bills.

I'd seriously consider a petrol hybrid as my next car, battery technology is slowly evolving to last longer and maintenance/running costs are pretty good.

whinny and over-revving. Why don't motorbikes last 100,000 miles

Utterly different type of engine!

This isn't a brexit thread, you are simply wrong, as the actual data shows!

You may imagine it to be whiney and over-revving, but that's your fault for driving it that way. If max torque is at 1,500rpm why would it be high revving for goodness sake?

Ah, but the catch is you need to be doing the right kind of driving for the DPF to do its job properly.

Well, not really. It always catches soot, it's the regeneration that can fail.

There are two ways to burn off the soot - passive and active. Passive regeneration is what happens when you are driving down the motorway. The engine shifts the injection timing to increase exhaust gas temperatures and you're golden. Active regen is when it injects extra fuel post combustion to react with a catalyst in the DPF to burn it off. It does both of these as a matter of course. If they don't get completed then the car tells you, and if you continue to ignore it you ruin the DPF.

At no point to they fail to catch particulates or release them into the atmosphere.

jambalaya

@molgrips, whinny and over-revving. Why don't motorbikes last 100,000 miles ? See the Golf owner review above. Customer choice. I won't be buying a small petrol turbo. Fuel injected 2 litre for me in mid sized car. Mrs B's Micra is 1600 non-turbo and our Yaris was 1.3. I won't buy a bigger heavier car (Golf/A3 size) with a turbo version of those engines.

First off, good luck getting one. Most companies will be phasing out bigger displacement na engines in small/mid sized cars.

Secondly

whinny and over-revving.

In 6th at 70mph most of these cars are doing 1700-2000rpm max. Also off boost which is how they can deliver the bigger mpg figures.

itstartedwithakona - Member

yep, little petrol turbos are actually quite torqey.

Ford's 1.0 ecoboost delivers up to 200 Nm from 1400 rpm

That more torque than the 2.0 n/a in a Honda S2000!#

edit - mixing up my units, the 2.0 honda actually has 220 Nm, but still...

Without checking I would guess peak torque in the v-tec is probably well up there in the rev range. In addition to having plenty of torque you're also saving 50-100kg over the diesel.

hah.. (I think?) my thinking is in line with jamabalaya's "old skool" approach.

currently in a petrol 2.0 vtech for my 20 mile (each way) motorway commute.. tax is £15 [i]a month[/i]. considering a 2.0 bluemotion golf down the line. yes its diesel, but its high MPG will and will save me a grand over 5 years in car tax alone. (its £30 a year).

would obviously consider a decent alternative if it presents itself. basically need a 5 door hatch (potential for a littleun in near future, mrs is about to get a recentish 1.4 - 1.6 5 door polo), and my current bike carrier should fit most hatches.

(previous car to my type-s civic was a mk3 golf gti 16v, awesome car with reliability issues that made me bin it in the end. my first car was a NA 1.4 Polo Open Air - great fun...)

Just to comment on the larger NA v's small turbo debate...

I had the 2.0 normally aspirated mk5 golf (the old FSI), which produced 150 bhp. The 1.4 TSI feels very similar and despite producing less peak power, is only 0.4s slower to 60 mph, is quieter at motorway speeds and is about 25% more fuel efficient.

I don't find the 1.4 whinny. It has a quite a pleasing note during acceleration and it does not need to be revved hard, as all the power is available at low revs.

IMO, the 1.4 TSI is a superior engine to that 2.0 FSI in every respect.

They offer the A3 with the 150 bhp 1.4 TSI. I think that would be as close to perfect as I could get for my application (except, perhaps a PHEV).

Would definitely test drive, especially if the petrol is a Euro6 non-turbo model.
Had a couple of rental cars recently that had no poke to them whatosever, especially uphill. One was an Astra (1.4 I think), another was an Insignia, with the only engine in the entire range that does not have a turbo. Had to rag that one in 2nd to drive up a hill just to sustain speed, and it was still telling me to upshift.
Had a VW polo that needed a downshift on every motorway/A road incline, but a VW golf that did not (both petrol, both smaller engine than my Leon 1.8 turbo).

[quote=andytherocketeer ]Would definitely test drive, especially if the petrol is a Euro6 non-turbo model.
Had a couple of rental cars recently that had no poke to them whatosever, especially uphill. One was an Astra (1.4 I think), another was an Insignia, with the only engine in the entire range that does not have a turbo. Had to rag that one in 2nd to drive up a hill just to sustain speed, and it was still telling me to upshift.
Had a VW polo that needed a downshift on every motorway/A road incline, but a VW golf that did not (both petrol, both smaller engine than my Leon 1.8 turbo).

Second this. Just got a Fiesta 1.25, it's notably gutless at low revs compared to the older model with the same (but pre-EURO6) engine.

can someone explain the difference between a PCP and a PCH please?

The last P in PCP means Purchase - you have an option to buy the car at the end of term. H in PCH is hire - you never own the car.

And with PCP you can sell it. Ok, it'll show as having finance secured on it, but a personal loan to pay off the finance, and then sell the car, does give you a get-out if you really need it.

To get out of a lease, you will be making all the payments remaining.

To get out of a lease, you will be making all the payments remaining.

Not necessarily true. You would need to look in to the T&C's of each specific deal. There are examples of early termination fees in the order of 50% of the outstanding payments. As stated previously, you cannot necessarily walk away from a PCP without incurring some penalty.

As with any finance, you need to ensure that you understand the implications of all the 'what ifs'.

NA vs Turbo'd cars is the way of the world

See 911s, where the 'turbo' model is just a faster version now, as the historically NA'd 911s are now turbos too

See also M5s and M3s, which are now turbo'd. See also all fast cars, hyper and super cars

Turbos give more power/torque for more/less mpg/CO2 - it's the way the rules are taking it

Motorbikes are different, and no CO2 palava applies to them (yet)

I'd also rather than a big NA rather than a smaller turbo, but the smaller turbo engine actually drive surprisingly well, largely due to peak torque being pretty good and low down the rev range

Okay I have not read all the replies above but I would choose ...

Japanese petrol automatic gear with at least 150bhp (125bhp is good enough for me).

chewkw - Member
Okay I have not read all the replies above but I would choose ...

Japanese petrol automatic gear with at least 150bhp (125bhp is good enough for me).

That would make a reasonable commuter motorbike.

I chose British petrol automatic with 380bhp.

benp1 - Member

NA vs Turbo'd cars is the way of the world
........ [b]See also all fast cars, hyper and super cars[/b]

Just to be a massive pedant - LaFerrari, Porsche 918, Lexus LFA, Ferrari F12, Lamborghini Aventador & Huracan, Audi R8, Viper ACR....Porsche 911 GT3RS....loads of normally aspirated fast cars /pedant.

Me and the Mrs recently bought a second hand Ford Focus petrol 1.0 Ecoboost 125ps (1 year old, 14k on the clock). The high gearing and very high bite point on the clutch took a while to get used to but the performance is incredible for such a small engine. The acceleration and pull is on par with the Ford Fiesta 1.8 turbodiesel I used to own from 2004-2008. Its performance surpasses that of my last car (1.6 petrol Focus estate).

Doing motorway trips to see friends / relatives we get an average of 45mpg. Using Shell fuel I've had that up to 52mpg before. For short trips around town that comes down quite considerably to 37-40mpg.

Neither of us do the mileage to justify owning a diesel engine, and we have friends and relatives that have been left with high maintenance bills on diesel cars due to filter / injector problems from not being run enough.

Buying new on PCP I'd pick the one I liked best, unless it was clear cut (i.e. 20K plus motorway miles).

Most of the servicing disadvantages (failures really) of diesels kick in at the sort of age I buy - DPF, DMF etc. - under 5 odd years you'd be unlucky to encounter it.

Just bought (post head on crash from a charming gent on the wrong side of the road) a new car for Mrs B, and went 1.4 petrol for simplicity (only spending 3K) of ownership and serivcing. Reasonably frugal too, if I'm not driving it.

Now that's not to say they are as clean as petrols, but the new tech is much better.

That's largely true of HGVs and buses, but real-world testing strongly suggests that modern diesel cars have made only very small improvements over their predecessors.

bensales - Member
That would make a reasonable commuter motorbike.

I chose British petrol automatic with 380bhp.

My 2005 1.6 litre petrol automatic gear Toyota Corolla has 120bhp with max speed of 109mph (I think that's the max speed) which for me is enough as I don't really drive fast.

380bhp? Jaguar?

That's largely true of HGVs and buses, but real-world testing strongly suggests that modern diesel cars have made only very small improvements over their predecessors.

You know the newest VAG engines have SCR and need AdBlue like HGVs don't you?

You know the newest VAG engines have SCR and need AdBlue like HGVs don't you?

Yes. Did you know that there are 2016 VAG cars emitting up to 6 times the Euro 6 emissions limit for NOx?

When you say removes it and when you say data You really mean makes it undetectable.

Vehicle industry staying 1 step above those doing the measuring.

Mean while the smaller particles linger in the air longer and are more harmful than the clod of black smog that comes out the back of my landy and gets taken to the floor almost instantly due to its weight.

Why don't motorbikes last 100,000 miles ?

Same reasons cars don't last 30-40 years either, I'd expect.

chewkw - Member

My 2005 1.6 litre petrol automatic gear Toyota Corolla has 120bhp with max speed of 109mph (I think that's the max speed) which for me is enough as I don't really drive fast.

380bhp? Jaguar?

Yes, new XF-S. 40th birthday present to myself.

I don't tend to drive fast either, I just like big saloon cars with powerful engines. Lazy cruising.

Did you know that there are 2016 VAG cars emitting up to 6 times the Euro 6 emissions limit for NOx?

Are they the ones with scr?

Cougar - Moderator

Why don't motorbikes last 100,000 miles ?

Same reasons cars don't last 30-40 years either, I'd expect.

Modern Japanese bikes will happily last 100k, just most people don't ride them that much.

Modern petrols seem to be much less economical than they should be given developments over the years.

Over 40 years ago I was getting 50 to 55 from a 1.3 Renault 5 which pulled well low down and would also register over 100 on the speedo if one was bothered to try.

I recently spoke with a Fiat Panda owner who said that due to all the emissions "stuff" on it it needed to be booted everywhere and returned only 35 mpg. More petrol used equals more pollution (at that sort of difference) surely.

There are advantages to diesel that I have never seen discussed. Better consumption means less oil reserves used up and (to my layman way of thinking) there must be a fair bit of pollution generated by the additional processing to produce petrol rather than diesel. Perhaps an oil expert can enlighten us.

Better consumption means less oil reserves used up

Well I'm not an oil expert, but I can have a stab. When crude oil comes out of the ground, it's a mixture of loads and loads of different hydrocarbons, with different configurations of carbon, hydrogen and oxygen. So for example methane (1 carbon 4 hydrogen or CH4) is a gas, athane C2H6, propane (which you'll have heard of) C3H8, butane and so on, including octane, which you'll also have heard of and is a liquid. But there are loads more besides, all the way down to thick tar which is almost solid.

Oil refineries separate out all these chemicals. So a barrel of crude contains X amount of the chemicals that make petrol and Y amount of diesel. But you refine it all in one go, so you automatically get a set amount of each fuel - and also heating oil, LPG and so on. Crude from different places contains different amounts of each. So it doesn't take any more to produce petrol than diesel.

Well - that's the theory. Diesel used to be cheap because we weren't using a lot and it was going spare after we extracted the petrol. But now manufacturers have produced lots of diesel cars demand exceeds supply a bit. So they have to take the heavier oils and split them up to make diesel. This takes quite a lot of energy so sometimes there's more energy being consumed than your MPG would indicate....

Thisisnotaspoon can explain more if he comes on.

Over 40 years ago I was getting 50 to 55 from a 1.3 Renault 5 which pulled well low down and would also register over 100 on the speedo if one was bothered to try.

Modern cars of a given size are far heavier. I get 50mpg on A road driving in my 1.4 petrol Octavia. Which for a car of that size and weight seems pretty good. Will also do around 127mph.

My main problem is the difference between fuel consumption when driving a vehicle hard between diesel and petrol, I manage 30 mpg out of my 2.9 lt 2.3 ton diesel when driving briskly and manage the same out of my wife's 1.6 petrol Megane driven in the same manner!

The other difference is how modern emissions are strangling smaller petrol cars, again my wife's car is far less responsive than my earlier 1.7lt carb fed Renault 5. 115 bhp 900 kgs, v 115 bhp 1.3 ton, 16 valve. The carburettor fed engine is so much more flexible and more lively.

I was always of the opinion that there is no replacement for displacement, but having downsized my other half's car from a 330 (3l, 6 cylinder) to a new MINI Cooper with a 1.5l, 3 cylinder turbo I've been really impressed with it. It's obviously not as fast because its a lot less powerful, but it's nippy, holds it's own on the motorway but is also very refined. It's quieter cruising than my diesel vRS. The current Cooper engine is much better than the old 1.6 N/A one to drive and in terms of economy etc.

When it came to replacing my company car last year, I wanted to go petrol however the lease deals still heavily favoured diesel cars which meant that my budget went much further in terms of spec etc despite the actual retail costs being higher.

jimjam - Member

benp1 - Member
NA vs Turbo'd cars is the way of the world
........ See also all fast cars, hyper and super cars

Just to be a massive pedant - LaFerrari, Porsche 918, Lexus LFA, Ferrari F12, Lamborghini Aventador & Huracan, Audi R8, Viper ACR....Porsche 911 GT3RS....loads of normally aspirated fast cars /pedant.

I wasn't that fair so you were right to call me on it

I think I'd summarise that turbos used to be used for extra power, now they're used for better efficiency (as well as extra power)

But NA supercars are a dying breed. Our kids will be driving hyper-e-cars

Motorbikes are safe from the emissions shenanigans at least - 1 litre engine, no turbo, 180 bhp

Yes, new XF-S. 40th birthday present to myself.

+1 for the new Mini Cooper 1.5. My OH has one - it's a superb engine, smooth, fast-ish and very economical (45 mpg + on a 20 mile commute. Computer pretends that it's 55!) Makes a lovely noise when you cane it, too.