[Closed] Petrol vs Diesel

I like the way diesels drive.

Modern diesels can also often be more expensive to service as well. I much prefer how a petrol delivers its power as well. Petrol engines have got pretty good on the fuel consumption front these days so with diesel costing more per litre as well, make sure you do the sums on the particular models you are looking at.

[url= http://www.googlefight.com/index.php?lang=en_GB&word1=petrol&word2=diesel ]Googlefight[/url]

Thats the thing, we'd be doing a few short journeys during the week but then I miss looking down and seeing 55mpg+ on my old Mondeo (vs 35mpg on my Octy vRS). Hmmm...

I also find if you have a heavy right foot, the gap in efficiency between petrol/diesel grows dramatically.

At worst my a3 does 40ish to the gallon. I could get my old golf to low 20's quite easily...

Diesels don't like lots of short trips.

9k miles per year is not massive, so questionable if there would be any savings.

less to go wrong on pertrol engine (V modern diesel) and cheaper to fix when it does.

I would go petrol in your situation.

I love my diesel but I'd buy petrol next. Cheaper at the pumps, cheaper to buy, better for your short runs. No point in the diesel as the through life costs are not worth the slightly better mpg on a long run.

This was my approach

-Diesel will be cheaper to run.
-No reason why a diesel shouldn't be used for short journeys.
-Less chance of a big bill with a normally aspirated petrol engine.
-Big Petrol is more fun (much more fun)

I have a 1.9tdi and 3.0l petrol. The tdi is mainly a round town runabout.

Depends on budget too. As they get older you might start to have issues with DPF, DMF, EGR, sooted up swirl flaps, high pressure fuel pumps, worn out injectors etc etc.. Not such an issue if buying new/nearly new.

I usually buy cheap cars, cash, 7+ years old, i'm not getting diesel again.

I personally would never go back to a hateful petrol engine, have been diesel now for 15 years and love the way they drive, reliability etc.

I wouldn't dream of buying a new car, have always bought mid-life to elderly cars and in that category I don't think there's a lot of difference in cost. I easily get 50+ mpg, which is great and I figure that is hopefully a lot less CO2. Mind, hardly use a car anyway.

Just my views.

For your mileage & description of journeys, I'd get petrol.

ill only go back to petrol with a big clunky engine (3l + )

driving the girlfriends 1.4 golf atm as the vans in the garage and you have to make the blighter sing for its supper despite having about 20/30 more bhp than my van.

"No reason why a diesel shouldn't be used for short journeys"

and what makes you say that ?

Petrol for me, and decent sized ones can be bought for peanuts - esp. compared to equivilent aged/mileage diesels.

X-Type 3.0i currently.

br - im thinking the same as you , if my mechanic tells me my gear box is shot im off out to look at a few not very old 2.5 non turbo subaru outback/foresters that can be had for peanuts cos abody wants the turbo

Do the maths, pick your choice of car, then work it out how much 9000 miles is for a diesel & how much for a petrol, then look at the prices of the cars & see whats the best for you. Also make sure you add in the road tax costs.

FWIW I swapped an identical petrol car for its diesel brother the gain was only about 10mpg, 28-30mpg petrol 38-40 mpg diesel, but thats a huge % difference even given diesel prices.

For 9000 miles a year you'll struggle to see any financial benefit from a diesel. Last time I did the maths I was looking at 20000/year for 3 years before it paid off.
Diesels and short journeys; Big heavy old lump takes longer to warm up. It was 7,5 miles to work for me and I didn't feel any heat for the first 4 in our diesel. The replacement petrol is pushing warm air out after a mile
Secondly, don't short journeys clog up the EGR valves?

Servicing costs more. Even a basic oil change is £15 cheaper because I now don't need fully synthetic oil for the turbo any more. We were lucky and our diesel was a good one and cost us no more in repairs than the petrol car that replaced it, but if something does go wrong the chances are a petrol engine will be cheaper to repair
Then there's the incidental costs people don't factor in; Diesels are generally heavier and also a lot torqueier, and that means you get through tyres quicker. I'm getting 6000 miles more from a comparable (same brand) tyre on the front if the petrol than I was on the diesel. Apply the same to suspension and brake parts too....
Also, for an engine with comparable power, the petrol will be smaller capacity, so our insurance went down too, by a fair chunk.

Yes, for some reasons diesel makes lots of sense. Big miles and towing, certainly. But you gotta do the sums based on your own situation

the yearly mileage thing with diesels vs petrol is a not the best way to look at it. I mean you could only be doing 9000 a year, but if you keep the car for 10 years thats 90k, which should be well past the break even point for petrol vs diesel

Look at the total mileage over the life you will keep the car rather than just the per year figure.

Can't be arsed googling it just now but I did find an online calculator that worked out what whether petrol or diesel worked out cheaper based on listed prices of the cars, current fuel prices and your mileage. I guess it's just an estimate, but it will give you a far better one than doing the maths yourself. Probably.

The parkers website has a great little calculator where you can pick 3 cars, thier age on purchase, your annual mileage and then how long you'll own them and gives you a great breakdown on what you likely costs will be (fuel, servicing, tax, etc.).

I was originally looking at a diesel focus estate, now happily driving a subaru legacy!

for short journeys then petrol must be the logical choice, can't see why you think diesel.

plus diesel is now officially a carcinogen, and diesels chuck out more under acceleration, so I also wouldn't think that was a good environmental choice.

I like petrol engines though, much more lively than a diesel. Feels more like the car has a heart to it...

After having a diesel for 4 years I went to a petrol, I hated it. I just prefer the way diesels drive. I have had some issues with well known faults such as DMF etc on one car but the other two have been fine. My diesel isn't that economical (45-48mpg) but it's nippy and I just like the way it drives. Just my opinion

All depends what you're looking at buying. Thought I was going to be getting a petrol this time, due to all the reasons mentioned above and because my annual mileage has now dropped below 10k (and unlikely to go much above 12k again in the near future), compared to ~20k when I last bought. However I'm doing a search without specifying engine type and all I'm coming up with for what I want (Mondeo estate ~4yo) is diesels - with the very occasional big thirsty automatic petrol for just as much money.

I like the lazy, slow punching feel of a big diesel... And a small diesel for that matter. Then again, I like vtwins for motorbikes so I guess that's the same appeal. It's like the difference between being fired from a trebuchet vs shot from a cannon.

The economy arguments are pretty thin these days I reckon, though mine is cheaper to tax than equivalent petrol cars, it's not a huge difference.

For 9000 miles a year you'll struggle to see any financial benefit from a diesel. Last time I did the maths I was looking at 20000/year for 3 years before it paid off.

This would entirely depend on the price difference of the 2 engine variants of the car. On some cars that difference may be very small, & paid for in only a few miles/months.

There IS a reason not to use diesel for mainly short trips. The insides get all coked up and they break, unless you give them a proper run more than occasionally.

As for 'slightly' more economical - my Passat 2.0 TDI auto gets over 60mpg on a motorway run at 70mph in the summertime - up to 65mpg if it's up the M5/M6. That's easily 30-40% more than the petrol equivalent I reckon.

The purchase cost need not be an issue - just by one or two years older. That needn't be an issue these days, the car's individual history is much more important than its age in terms of reliability and condition.

The only thing I worry about is the risk of expensive fuel system issues. DPFs and turbos shouldn't be an issue if you keep the oil up and don't neglect the long trips.

I'm getting 6000 miles more from a comparable (same brand) tyre on the front if the petrol than I was on the diesel

This is about how you drive though. My tyres were on 10 or 20% worn after at least 10k miles, and that was with some caravan towing involved too. Brakes - had the pads changed after I think about 55k miles.

If I look at the rest of the VW range there are 2.0 petrols which are pretty uneconomical, then there are 1.4 petrols which are seriously gutless. The TFSI engines look great but the are turboed too which reduces the gap in potential failure cost.

Here we are Chaps........all you ever wanted to know!

http://www.honestjohn.co.uk/faq/diesel-vs-petrol/

Here we are Chaps........all you ever wanted to know!

http://www.honestjohn.co.uk/faq/diesel-vs-petrol/

Glowplug failures up to £1,000 if they come out. Up to £3,000 if they snap and the head has to be removed to extract them.

Well John might want to know that there's hardly a modern diesel that uses glowplugs.

Diesels and short journeys; Big heavy old lump takes longer to warm up. It was 7,5 miles to work for me and I didn't feel any heat for the first 4 in our diesel. The replacement petrol is pushing warm air out after a mile

A mile? My Diesel yesterday was pushing warm air out the vents after about 10 seconds thanks to climate control that makes so little difference to a diesel I can use it without concern.

£3000 for glowplugs? You wot?

Glowplugs are a few quid, now I know there could be access issues, but do me a favour.

The tone of that 'article' is very anti-diesel, I'd take it with a pinch of salt.

Exactly Molgrips I know he's talking about them snapping when taking them out but same could be said for those spark plug things engines once used but they went around the same time as glow plugs.

i have a 2.0 tdci mondeo, it does 50mpg, the WORST ive had out of it is 42mpg. (round town, all short journeys, aircon on full blast)
my mate has a 2.2sri vectra, admittedly, it is a little quicker away from the lights, but it does 27mpg average, the BEST hes had out of it is 45mpg, temporarily, cruising at 50mph on the motorway.
i will also say, on a motorway my mondeo is a lot quicker to get going after a hold up (more torque).
i like the way diesels drive, more relaxed.
BUT, for my next car i will do my sums before deciding whether to go petrol or diesel, if the petrol car is 2k cheaper to buy but only does 10mpg less, it will take a fair while to recoup the extra cost of a diesel.
my car has 150,000 miles on it, with routine servicing/normal wear and tear items replaced only. (ie, its never broken down)

The only difference between glow plugs and spark plugs is that engine designers know spark plugs are going to be changed at some point, so they make them accessible. Glow plugs are also a service item though so they SHOULD be accessible. On my old engine two were a piece of cake, one was awkward and the last one cost me the price of a long 8mm ratchet spanner, a lot of skin from my knuckles and a lot of time since I could only move the spanner enough to do one click at a time!

My choice of fuel is petrol hybrid, having driven two different styles. No round town problems and good economy on the motorway too. Only reason I have one diesel car is the requirement to tow.

I have driven a couple of modern small engined petrol cars and got no better than 45mpg, which is a bit crap considering they were tiny and the eco variants too.

The last diesel I had with glowplugs I replaced them myself, was a doddle. Mind you that was about 12 years ago now as not had any since with glowplugs.

Here is my 5p's worth, wife had a bmw 118d which we kept till she had done 100,000, never missed a beat but with her 26,000 miles per year we never managed to get more than 43mpg combined( I used brim to brim method) and struggled to get over 46 on a long run, so I bought her a vx tigra 1.3 cdti/fiat engine diesel and she now easily gets 60mpg, which worked out to be about £600-700 a year fuel saving.
I kept the bmw but I only drive about 3000 miles and mostly town driving when taking my daughter out and was struggling to get over 36mpg and I drive very efficiently and being a worry wart knowing about dpf's etc + short journeys and combined with swirl flaps etc I knew my driving would be doing the engine any favours so I chopped it in for a low powered 1.4 petrol 207sw, best decision ever, I get 40-42mpg round town and have just had 56mpg over my trip to Wales last week so its actually cheaper on fuel,granted I drive gently and don't speed so our choice is petrol for me, diesel for her, not sure that waffling of mine helps you decide but its how its been for us 🙂

If I were buying used under £4k I'd buy petrol on the basis it will be better condition/lower mileage. Generally diesels hold their value despite high mileage. Higher mileage means other bills for maintenance like wheel bearings, suspension, Dual Mass Flywheels etc..

I recently swapped from an old skool diesel vectra (45-55mpg, PeterPoddys old car) to a petrol vectra 2.2 (35-37mpg). The cost per mile in fuel is only 2-3p more in the new car. However it was less than half the price of buying the same model/age/mileage with a diesel engine. For me £1.6k got a 85k mile 04 plate car, it was £4k to get a diesel!

If I were buying new I'd get diesel, mainly due to them holding their value better.

This is about how you drive though. My tyres were on 10 or 20% worn after at least 10k miles, and that was with some caravan towing involved too. Brakes - had the pads changed after I think about 55k miles.

Well, that's me driving the 2 cars on 90% motorway, so the driving is the same. So yeah, it can be, you're right, but this is as good a comparison as you'll ever get.
Brakes - ours is still on the original pads at 66,000 miles, if you want to get into one-upmanship! 🙂
Don't get me wrong, I'd have a diesel if it would save me money, and if I'd have known I was going to be travelling for 18months again, I'd have bought another as they make good motorway cars IMO, but I didn't know that at the time we changed. I did the maths then, based on the info available at the time (use, fuel prices, milage etc) and I couldn't split the two by more than £100 or so a year. An as I prefer petrol engines that's what we got.
There's a good chance out next car will be a diesel to be fair, for various reasons, but we keep our cars a looooong time, generally 5-6 years, so that won't be for a year or two yet.

martymac - your mate must be thrashing that 2.2SRI. As mine gets 10mpg more than him on average. Worst (cental London driving) 33mpg.

In my experiance it is generally that a diesel can be thrashed and get good mpg. A petrol requires some more care to get a reasonable mpg, but that doesn't always mean driving slowly to achive it.

I recently swapped from an old skool diesel vectra (45-55mpg, PeterPoddys old car

Hi mate, did our old Vectra work out OK for you then? Was a good old barge on the motorway was that car. You must have kept it, what, 3 years or more?

Yeah, it worked out really well thanks. Put 50k on it, took it to the alps and south of france too! Best value for money car I've owned so thanks for letting me have it for such a good 'mates' rate.

Ended up selling it on after a decent insurance pay out due to someone crashing into it (very minor scratch), kept it for a bit more while looking for a new car and chopped it in. It's still being driven around today!

Yeah, it worked out really well thanks. Put 50k on it, took it to the alps and south of france too! Best value for money car I've owned so thanks for letting me have it for such a good 'mates' rate.
Ended up selling it on after a decent insurance pay out due to someone crashing into it (very minor scratch), kept it for a bit more while looking for a new car and chopped it in. It's still being driven around today!

Glad to hear it! 🙂
That price was simply £100 more than the trade in value we were offered (as i think i said at the time) Those 2.0dti engines are as solid as a rock apparently. One of the more reliable diesels around. 🙂

There's a good chance out next car will be a diesel to be fair

Out of interest, why's that?

Well, the car I'd like will be silly expensive to run with a petrol engine. Either that or silly expensive to buy with a newer, more sensible, petrol engine.
But I dunno. It's a long time away yet.
I want an Alfa Romeo. No. Scrub that. I NEED an Alfa Romeo. But there's not many that fit what we need. 98% of the time we would be fine with a GT. The rest of the time we'd need a 159. I'd be happy with either.

You mean you want something faster which would be too thirsty in petrol form?

Personally, if I could afford it I'd get an A6 with the 3.0 V6 TDI and CVT auto. Super relaxed torquey cruising, loads of power, and still 50mpg. Supposedly anyway 🙂

@ solamanda,
yeah, he does thrash it a bit, more than i do with mine certainly.

If you're buying a new company car and someone else is paying to fix it, then it's diesel nearly every time.

For personal use, I'd go petrol. For some cars the price difference is bonkers - ie, BMW 320d Cabrios around 2004 go for about £6-7k. 320 Cabrios go for about 4-5k. Add in the complex bits - EGR, DMF, DPF, new turbos etc. and you're prety much guaranteed a big bill. I'd much sooner hand over an extra £5-£10 a week on fuel than chance a £500-£1000 bill out of the blue.

Some of the folk on here are comparing really poor petrol cars with decent diesels too, which is rather muddying the waters. For instance, the 1.4 Golf is an abomination - the 1.4 engine struggles pulling a Polo around...

You mean you want something faster which would be too thirsty in petrol form?

Sort of.

But at the end of the day I want an Alfa. A red one. That's all. Simples. 🙂
I don't really want a diesel. If it was for me alone I'd have a 3 litre V6 or 2 litre twinspark.
But there's more than that to consider.

Although, that said, I'd rather spend £3000 or less on a nice v6 or TS than double that or more on a newer diesel
Diesel in an Alfa is like a moustache on the Mona Lisa. But we won't go there, eh? 😉

There's a decent 1.6TS 156 for sale near us for £600 actually. That would do me if it wasn't blue.

My tuppence after having to endure 600miles in a diesel this weekend.

Petrol - floor it and revs x torque = power; simples! If you try and set off from 20mph in 5th of course nothing happens, knock it into 3rd though and shit leaves the shovel.

Diesel, floor it, and the engine thinks about it, makes a whirring sound, anddddddddddddddddddd nothing. Then you drop a few gears, floor it again, it thinks about it, makes a whirring sound and then sets off like an overweight Labrador, then you run into the rev limiter at 4000 and have to repeat the process again.

The saving grace of diesel is it seems to do the same mpg whether you thrash it or cruise. This is a product of slightly more efficient combustion and the above mentioned turbo lag means that airflow is only vaguely correlated to what your right foot is doing, if you built in throttle response that slow into a petrol ECU it'd probably be efficient too.

[i]Petrol - floor it and revs x torque = power; simples! If you try and set off from 20mph in 5th of course nothing happens, knock it into 3rd though and shit leaves the shovel.

Diesel, floor it, and the engine thinks about it, makes a whirring sound, anddddddddddddddddddd nothing. Then you drop a few gears, floor it again, it thinks about it, makes a whirring sound and then sets off like an overweight Labrador, then you run into the rev limiter at 4000 and have to repeat the process again.[/i]

you need an auto Mate

Or needs to learn that diesels are not petrols and petrols are not diesel......

Drive em differently .... Diesels are lazy mans cars. Petrols are for folk who like changing gear

thisisnotaspoon - Member

Diesel, floor it, and the engine thinks about it, makes a whirring sound, anddddddddddddddddddd nothing. Then you drop a few gears, floor it again, it thinks about it, makes a whirring sound and then sets off like an overweight Labrador, then you run into the rev limiter at 4000 and have to repeat the process again.

Try some better diesels.

Also, an observation... Sometimes I do need to knock mine down a gear or two from cruising to overtaking. The reason for this is that it can cruise along at about 1200rpm. Now that's not a "problem" you'd have with an equivalent petrol car, because it wouldn't let you do that in the first place- you'd have to be carrying more revs.

Thing is though, this is an extra capability that you don't have to use- nothing to stop you driving a diesel up in its power band, at which point you'll have more immediate response.

O[i]r needs to learn that diesels are not petrols and petrols are not diesel......

Drive em differently .... Diesels are lazy mans cars. Petrols are for folk who like changing gear.[/i]

Get a 3 litre V6 petrol and there's not a lot of gear changing required. Unlike the wifes V50 Sportwagon 2.0D which is okay, but you gotta be in the right gear.

Recently bought a passat diesel, and engine responds very nice indeed. Got to love diesels. Oh and it purrrs like a Cheshire Cat too! Used to drive petrol accord, it was good car etc but I don't like characteristics of petrol engines. I get pain in my ears to hear engine scream. Unless if it was V8 but then if you drove diesel V8 that would be entirely different story. I would say one thing for sure, seeing fuel gauge going down so quick irritated me most. Now things went from 30mpg to 50mpg and that is encouraging to more adventures.

Petrols are for folk who like changing gear

I like changing gears in my diesel and that's coming from a SS 😉

Tinas - either you had a rubbish diesel or you have no idea about driving them. I've never driven a diesel that did that. In fact one reason I like driving them is that they are the opposite. Ease down the pedal and you go whooshing away regardless of gear.

Was it a 1.8 tdci? They are famously bad. Or was it an econetic one? The VW equivalent are mapped with a lack if torque at the very bottom end I think.

And as for V6 3.0 petrols, they are nice to drive, no arguments there, but they aren't cheap and would be doing well to get half the mpg I do. Not really a like for like comparison!

tinas - you were either doing it wrong or it was a very underpowered diesel that was never going to be quick.

fwiw I had the same experience sat in the passenger seat of my bro-in-laws 320i this weekend. He was driving everywhere with the rev too low so it was accelerating like he'd hitched up a tractor to the back. Had he been driving a 320d, progress would have been brisker. I think he is still in the mindset of driving their Polo tdi.

The whole run out of revs thing makes no sense, either. Generally diesel are geared longer to take advantage of the torque.

Decided dizzle is the way to go 🙂

90% set on a Mondeo ST TDCI (still) / 10% of me wants to go and have a play in a newer shape Mondeo Titanium X. Both can be had relatively cheap with low enough miles for me to not to have to worry about DMFs etc for another 4 or 5 years (doing our current mileage) and the petrol equivalents aren't that much, if any, cheaper (apart from the ST220 but I'm not getting a 3L V6).

The last time I drove a diesel like the one Tinas mentions the turbo pipe had come off, that is certainly nothing like the last few diesels I've owned. I still don't get this you have to drive them different thing, I drive them both the same but then I drive them like I was taught during Police driving training, we used the Police driving course when I did mine.

you dont HAVE to ...but it helps......

if you have a petrol with enough power (as most police cars will be) then its a non issue... my 3.5 v8 drives similarly to my 1.9 diesel...but has 165bhp and does 4-15mpg compared to the 80 bhp and 45mpg of the diesel....

trail_rat - Member

Petrols are for folk who like changing gear

How about petrol with automatic gear? I got one and enjoy it very much. It's a 2005 Toyota Corolla 1.6 auto and it's fast enough to hit 70mph. Fuel consumption is around I think 30mpg.

Manual gear is sssoooo yesterday ...

😆

if you have a petrol with enough power (as most police cars will be) then its a non issue.

Well I don't drive those but have you seen most Police cars?

I'm talking about my own cars, work vehicles which ranged form Renault Masters, Ford Transits although that was moons ago, Discovery, Focus and others. Drove them all the same as we were taught use the gear through right through the revs and often skip gears when going up. Both petrol and diesels were fine and drove pretty much the same.

I've haven't got any proper figures, but I recall a piece on Top Gear (before the buffoons took over) comparing used cars petrol v diesel.

Comparing the extra cost for a deisel model (same spec) and then the quoted, not real world, fuel usage. You'd need to do 50k miles before the costs equalled out. I think this was on a £5k petrol v the £6.5k deisel cars, same spec car.

My thinking is deisel: more to buy, more at the pump, although you visit less often, more to service, more wear on service parts (brakes, suspension, tyres), better towing, better on longer motorway trips.

Back then when Top Gear was about walking around a car mumbling; the price differences, servicing intervals and deprecation of diesels and petrols were a world of difference to now.

I love the MPG I get from my diesel and love the torquey feel.

12,000 miles, 48mpg, 0-60 7.1 sec, 185hp

That's 48 MPG mainly city driving in London and I rag it as much as possible - I usually get 55mpg-ish on long runs. Best I have done is London to Bournemouth with a 62mpg average over 100 miles.

2012 BMW 120d

Congratulations, you're 23,000 pound car has saved you 3-400 each year compared to a car that does 35mpg. The first years depreciation is over 4000 pounds btw.

(Sorry, I probably sound slightly bitter, but i just had to change a DMF and it wiped out over 2 years fuel savings.)

The saving grace of diesel is it seems to do the same mpg whether you thrash it or cruise

Myth. How can it?

I wish mine did I would get my record of 92mpg then.

The thing is with mpg figures is that people believe their trip computers and only ever look at them now and again anyway.
I'm a fuel geek. I've been recording every tankful in most cars and bikes I've owned for 20 odd years. Solamana will confirm this as I gave him 50,000 miles with of records with the Vectra as mentioned earlier (44-45 average IIRC)
Now I do it all on a phone app. I can look at the graph it generates and tell you why the figure rose or dropped. I know, for instance, that fitting cruise control on the Focus costs me fuel. I'm more economical with my right foot than the electronics can manage.
That Vectra: take it easy 49mpg. Load it up with people, put 3 bikes on the roof and drive to Afan: 37mpg.
Work an engine harder and it uses more fuel. Fact.

^ I do the same PP. My OH thinks I am very sad. I agree with her, but I've done it for so long I can't bear not to...was averaging 54mpg until changing my driving style & slowing down to 60 on my commute. Now averaging 62+mpg. I wouldn't bother if I wasn't doing a 400 mile/week commute & I have to leave early to beat the traffic so driving at 70 just means I get to work even earlier.

I haven't experienced the whole 'diesel cost more to run' thing. Servicing is comparable to my last car; a 1.4 petrol Fiesta, tyres last ages, it's only on it's second set of front discs & pads (197k miles on it & the 1st set managed 119k miles), original clutch, original dmf, original turbo etc...anti-roll bar bushes need doing again, so they last about 100k miles.

Maybe i've just been lucky...

I've tested the car trip against my maths and found them to be so close it's not worth me worrying about doing the work myself.

Stumpy, yeah agreed! 🙂
Like I said, our diesel was fine too. It's just the big 'IF' it goes wrong I think!

I know, for instance, that fitting cruise control on the Focus costs me fuel. I'm more economical with my right foot than the electronics can manage

Hmm.. this is a debate that raged for a while on the Prius forums (yes you may hate the car but PP they are even worse fuel geeks than you!).

In my experience, if it's windy then cruise is worse, but if it's open ie motorway then cruise is better.

It's difficult to maintain exact speed on a motorway by hand (or foot), and slightly slowing down and slightly speeding up all the time reduces MPG - even if it's not enough to notice. If I ease down ever so slightly on the pedal, so gently that you can't even tell, the mpg readout goes down loads. More so in the Prius, but it still applies in the Passat.

I use cruise all the time when the road is open and not too windy/hilly.

In my experience, if it's windy then cruise is worse, but if it's open ie motorway then cruise is better.
It's difficult to maintain exact speed on a motorway by hand (or foot)

Now, see, that's the key. Steady speed. Lots of people can't keep a steady speed to save their lives and waste fuel as a result. (I think you can though Mol. I think you know what you're doing 🙂 ) so cruise saves them fuel.
But there's more to it than just a steady speed I think.
When I'm driving with my foot, I'll keep a steady throttle going downhill and speed up a bit. Maybe 5 mph or so. As I come to the rise the other side ill gradually slow down as I climb. So I might have chosen 65mph as my speed but increase it to 70 downhill and reduce to 60 on the way back up.

I think that's how I beat the cruise control: it uses more throttle to get up hills by keeping the speed constant.
It wasn't a big difference. 1mpg, maybe a bit more. But I definitely noticed it

Also, it's not OE cruise and its not that sensitive. That doesn't hell either.

Cruise on the mondeo is definately worse on uppy-downy roads, ime... Not it's fault, it can't predict the road ahead in the same way as a driver can, so it wants to power up the hills then immediately starts engine braking on the descents, rather than using the gradients.

On relatively simple roads it does seem better though. And certainly stops me from slowing into corners then deploying the lead boot on the exits.

Ah.. cruise does vary in accuracy yes. It's pretty good on both my cars, but on some autos I've hired in the US it's been poor.

It does save energy on resonable gradients as you say but I don't want to drive like that.. people varying their speed pisses me off! In certain situations without traffic beind me I have slowed up hills. The A30 I think over Dartmoor is so hilly that it's better not to use cruise. However 8 times out of 10 I am driving along the M4 which is looong gradients.

Another thing I do when there's not much traffic around is coast towards roundabouts etc. In the Prius it's possible to touch the throttle and roll without the engine turning at all, using electricity or even nothing at all depending on speed. On the A4042 with lots of roundabouts I gun it up to 60 then just roll to the next one.

Another thing I do when there's not much traffic around is coast towards roundabouts etc. In the Prius it's possible to touch the throttle and roll without the engine turning at all, using electricity or even nothing at all depending on speed. On the A4042 with lots of roundabouts I gun it up to 60 then just roll to the next one.

To be fair I'd like to drive a Prius to see what they're like.
What sort of MPG do you get? I'm assuming its free VED too?
But coasting, yeah, I reckon that's why I'm doing so well out of my auto Omega in part. It seem with an auto you can come off the throttle nearly 1/2 mile before a junction and it doesn't have the same engine braking and rolls on for aaaaages. I've said before on here that I think my style suits an auto. I like them. Always have done.

Just out of interest, what apps are people using to record fuel economy??

The saving grace of diesel is it seems to do the same mpg whether you thrash it or cruise

Myth. How can it?

@daveyboywonder - I just keep the receipt, write the mileage on it & then use a simple Excel file. Probably a bit of a heathen way to do it, but it works, I don't always have my phone with me & I've been using this method since before you could buy a smart phone...perhaps i'll swap over at some point.

Filled up this morning - 64mpg for the last tank...

Edit:

TINAS - turbo lag...really? If you are thrashing a diesel I assume you'd be keeping the revs high enough and turbo lag is virtually non-existent. A lot of people confuse turbo lag with the gutless feel of a diesel below about 1700rpm. That's not turbo lag, it's just that below a certain revs the turbo isn't being utilised. People who confuse this with turbo lag, normally stick their foot to the floor when the engine is doing 1200rpm & complain that nothing happens because of turbo lag. But it isn't lag from the turbo, it's just that the engine is effectively running NA until such revs are reached that the turbo comes into play.

Just out of interest, what apps are people using to record fuel economy??

Road Trip. Works very well. I think there's a free version to try too.