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Diesel Vs Petrol

131 posts & 42 voices | Started 6 months ago by mboy | Latest reply from molgrips

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mboy - Member

I've been kidding myself...

Last few cars I've bought have religiously been diesel "cos they're cheaper to run of course", or so I've told everyone.

Now my current car needs some work on it to get it through its upcoming MOT, about £400 worth to the suspension and brakes. It's worth about £2k, and being a 2.5L diesel averages about 35-36mpg. I've had a few 1.9L VAG diesels before, and with the exception of the Mk3 Golf TDi, none of them have come close to the stated MPG figures, even if I drive like a Grandad. This current 2.5L TDi Audi is the first I've owned to exceed the stated MPG figures (maybe cos it's a lot more powerful it doesn't need thrashing so much), but it has got me thinking...

My 2.5L diesel has 150bhp, about the same sort of power as most 2L petrol cars. Looking around for similar sized cars, most 2L petrol cars of similar size seem to come in at 33-35 mpg on the combined cycle, barely any worse than my Audi. But not only that, petrol is cheaper. But not only that, Petrol cars have WAY less to go wrong, and are much cheaper to service. But not only that (notice a pattern yet?), but you can pick up some pretty decent motors these days for not much money... £1k seems to buy you a lot of car right now if it's a petrol, and you'd have to more than double that amount to get a similar diesel powered car, which is most likely going to need a new fuel pump or turbo inside the next 12 months...

I know if you're doing big milages, obviously a new diesel (preferably with someone else picking up the monthly payments) is the way to go, but as my annual milage has probably more than halved recently going down to an estimated 10k from about 25k, I think the Audi is probably gonna have to go...

In fact, just spotted a 10yr old Mondeo 2L Zetec with FSH and only 53k on the clock on Autotrader for only £500! It might cost me £20 a month more in fuel, but I bet it'd save me more than that in servicing (and the same again in insurance probably but that's by the by), and I'd probably put £1k+ in my pocket once my Audi has gone (even after doing the work to it to put it through its MOT)... Besides, if it was scrap inside 2 years, it's got alloy wheels and a 2 litre Zetec engine, both of which are worth a couple of hundred quid to a kit car builder somewhere!

Posted 6 months ago #
TheFunkyMonkey - Member

I understand your thinking, i'm in the same predicament myself.

Currently have a 2002 diesel x-trail on 150k. The turbo has just started to whine a bit and the fuel pump is on it's way out, so looking at not much change from a grand for that. It's done 40k in 5 years, so the next car will be petrol. Looking at either another x-trail or a CRV. Need the space for camping stuff etc and the mrs works out in the sticks, so chunky tyres and 4x4 are really useful.

The x-trail averages about 40mpg, which is not bad considering it's the older 2.2DI engine, so ifi get 30 from a petrol, i can live with that, plus with the purchase saving,i can get something a bit newer with more toys

Posted 6 months ago #
TheBrick - Member

2.5L diesel averages about 35-36mpg

You must have a pretty heavy foot!

Posted 6 months ago #
spooky_b329 - Member

I much prefer the drive a diesel gives, but I'd agree a petrol is cheaper and simpler to run/service than a modern diesel.

The costs involved with injectors and dual mass flywheels just isn't worth it unless you are doing huge mileages. My wife's commute means that unfortunately she covers about 450 miles per week but when we changed our car we decided to ignore the diesels for once, and got a petrol to avoid any big unforeseen bills. Plus we avoided the premium that you have to pay for a diesel.

Posted 6 months ago #
metalheart - Member

Somebody I used to work with did check once and worked out that you needed to be doing about 25k before diesel pays back (from new). Isn't there some kind of calculator on some of the car websites? AA perhaps?

So if you are only doing 10k petrol should definitely work out cheaper (like for like).

I have 1.9 diesel octavia, I can get 50-ish out of it most of the time to work and back and achieve 60-ish regularly on longer runs. The bigger vag diesels aren't great as you generally have to boot them (and aren't audi's pretty heavy) to make them shift.

Edit: and someone will no doubt turn up in a minute and start banging on about DPF problems too, another reason to go petrol! Like the above post I prefer the way diesels drive too and getting 5-600 miles to a tank...

Posted 6 months ago #
spooky_b329 - Member

Anyone know of a calculator that gives payback for your average 5 year old £5k motor?

Posted 6 months ago #
aracer - Member

being a 2.5L diesel averages about 35-36mpg.

In an A4? I get 45mpg+ out of my 110bhp (when new ) 2L in a big 406 estate (frequently used at illegal speeds on motorways with roof loads). 35-36 is pretty awful for a 150bhp 2.5L IMHO. You'll get far worse than that with a similar driving style in a similar power petrol car.

It all depends on mileage though - at 10k a petrol ought to work out cheaper. I'm struggling with this one myself as my mileage has now dropped enough that a petrol ought to work out cheaper overall.

Posted 6 months ago #
Keef - Member

if the audi is a quattro,35-36 is about right on over all.40mpg on a run.
we've got-
Audi a6 tdi 180 quattro avant 7 seater,big heavy-35ish mpg.
VW passat 1.9 tdi 130.estate,50-60 mpg.
VW t4 1.9 800 special van,35-38 ish
two VW t25 1.6 td's-both get 35-40 mpg's.............

Posted 6 months ago #
carbon337 - Member

Dmf, turbo, egr, no more diesels for me. Sticking to Japanese petrols next time.

Posted 6 months ago #
tonyg2003 - Member

I'd agree with what you have said regarding petrol vs diesel. However I'd limit that to normally aspirated petrols not turbo/supercharged ones - again down to modern engine complexity.

BTW The price per litre gap between diesel vs petrol price was the highest ever this week.

Posted 6 months ago #
molgrips - Member

I've had a few 1.9L VAG diesels before, and with the exception of the Mk3 Golf TDi, none of them have come close to the stated MPG figures, even if I drive like a Grandad.

I get better than the 'stated' figures. I've got a 2.0l auto Passat TDI and the combined cycle test figure is 48mpg, I almost always get more than 50mpg average for a whole tank, sometimes 52. A motorway run can be up to 56mpg. Those figures are all at the speed limit. It drops to about 48mpg on an 80mph motorway trip.

If you are only getting 35mpg from a manual 150bhp then there is something badly wrong with either you or the car. I drove a hired Ford Galaxy 170bhp from Cardiff to Heathrow and back and got 46mpg. A larger and much less aerodynamic car with more power and I got a third more mpg. Something is wrong.

I agree that an extra 5mpg over petrol isn't worth it, but an extra 15mpg or almost 50% is, in my book.

Posted 6 months ago #
mboy - Member

You must have a pretty heavy foot

There's ALWAYS one! If I believed what the trip computer tells me, it would be 42-43mpg overall, but as I don't and I work it out myself properly, I know it to be accurate.

35-36 is pretty awful for a 150bhp 2.5L IMHO. You'll get far worse than that with a similar driving style in a similar power petrol car.

And then there's always aracer!

The car is an 11 year old A4 Quattro, quoted combined cycle is 34.8mpg, I've had as much as 38, but it's generally 35-36. 40+ is easy on a run though. Of course, a newer car would be more economical, if anyone wants to give me £10k plus for one they are more than welcome to do so!

Keef, would say you're about spot on on the economy figures there, except the 2 1.9 passat's I had, one got 45mpg, the other only 41 overall!!! Was shocked how bad they were compared to what I was expecting, the less economical one was on 17" wheels with 225 tyres though which might have made a difference.

Posted 6 months ago #
mu3266 - Member

I paid £14800 from new for my car & regularly achieve 60mpg or more depending on how fast I boot it. I regularly drive 450 miles a weekend (there and back) and very little other driving. Has anyone factored in the usage of biofuels such as cooking oil or rapeseed oil to lower their fuel costs. Some of the older diesel engines can accept over 50% with no issues.

Posted 6 months ago #
mboy - Member

If you are only getting 35mpg from a manual 150bhp then there is something badly wrong with either you or the car. I drove a hired Ford Galaxy 170bhp from Cardiff to Heathrow and back and got 46mpg. A larger and much less aerodynamic car with more power and I got a third more mpg. Something is wrong.

Bang on cue... Was waiting for you to come in waving your willy about!

I quote the REAL figures, not the trip computer Bollox. The car is also 11 years old, diesel texhnology has moved on. It's a 2.5L V6 in a 1600kg car with 4wd, that I'm acheiving better than the quoted mpg figures on, yet of course it's still not good enough for you!

Jesus, I wasn't seeking approval... I'd expect 50+ mpg in a modern 2 litre diesel Passat too, they're a more efficient engine (when they're working) than my older V6 is. I was merely trying to point out that despite what I've been trying to convince myself, on a budget (I've not bought a car for more than £2k in many years) a petrol car just makes more financial sense right now!

Posted 6 months ago #
weeksy - Member

This is all why i bought a Mondeo petrol recently.

£2000 got me a decent spec 1.8 petrol with 31,000 on the clocks... lol. Yes really.

I broke a mirror last week, £13 posted... i needed a power steering pump... £20 posted...

This is why my volvo S60 D5 was sold and i'm now running a petrol.

Basically if something MAJOR happens on a diesel, it can run £1500... if the worst case happens on the petrol... £450...

Posted 6 months ago #
Keef - Member

mboy,a very common problem on 2.5 v6 tdi VAG's is cam wear,in fact I'd say most of the older 6 pot tdi's will need new cams by now,this affects the economy quite badly. cams are around £400ish each from VAG btw,plus full gaskets,belts,tensioners,oil,coolant change etc,so not worth changing IMO.

ps,just for the record,I can get 63.2 mpg from the passat,on A and B roads,20 mile journey.but I have to drive it like a total granny !

Posted 6 months ago #
molgrips - Member

I quote the REAL figures, not the trip computer Bollox

What makes you think I don't check my trip computer?

I don't think the new diesels are more efficient than the old ones actually. Yours is the same tech as mine probably - the PD engine.

Jesus, I wasn't seeking approval

Approval has nothing to do with it, I was just pointing out that there could be something wrong with the car or the driving style. And to add a bit of balance. You've got a V6 4WD car and are banging on about poor diesel mileage. Well the problem isn't diesel, it's apparently 4WD V6s, which is what I was trying to say.

Posted 6 months ago #
b r - Member

My last company car was thrashed (I had a fuel card plus 35k pa).

Vauxhall Vectra 2.2i auto - 33mpg

So there is a guide for you, and over the 70k I ran it (from new) just had 2 services (£160 each), a set of rear discs and a four tyres.

My current car is a petrol (3.5i), and my next most probably will be.

Posted 6 months ago #
molgrips - Member

My diesel services are not expensive, so far - 80k miles. Nothing's failed yet, but the only shock expenisve service item was the DSG gearbox, which isn't diesel specific of course.

I'll wait to see if anything makes me change my mind.

Posted 6 months ago #
flow - Member

Be careful Mboy, rub Molgrips up the wrong way and he will get you banned.

I did exactly what you are on about. Had an Audi A3 2.0 TDI, sold it and got an A3 1.6 FSI. Its damn slow but not that much worse on fuel (infact it was better to Scotland and back), and like you said a hell of a lot cheaper to fix if it goes wrong.

No DMF, DPF, turbo, diesel pump etc

Posted 6 months ago #
vertical climber - Member

had a 1.6 petrol did 42 average where i drive, got a diesel 1.4 tdci 65+ average and 20 a year tax as opposed to 150 600+ a year saving overall
get the right diesel knocks spots off petrol

pre dpf as well

Posted 6 months ago #
molgrips - Member

I will get you banned? I've never reported anyone, if that's what you mean!

I'd be tempted by a TFSI* - they have good published figures but there's some doubt as to whether or not it's possible to get close. What mpg do you get from the FSI flow?

* because of the pollution issues and the issue of whether or not diesel has a worse carbon footprint than petrol due to manufacturing from heavy oil cracking.

Posted 6 months ago #
monkey_boy - Member

pre-posh DMF blah blah diesels are the way to go. we run a 1.4 & 1.6tdci fiestas

£30 quid tax a year 55+mpg, service them myself.

Posted 6 months ago #
flow - Member

get the right diesel knocks spots off petrol

Until something goes wrong, thats the whole point.

Unless you are doing loads of miles a year its pointless owning a diesel.

Posted 6 months ago #
molgrips - Member

I wonder what towing is like with a 2.0 TFSI? Should be good in theory.

I'd drive petrol hybrids if I could tow with one.

I'd love to know what the chance of a DMF, DPF or injector failure is inside say 100 or 150k miles...

Posted 6 months ago #
flow - Member

I will get you banned? I've never reported anyone, if that's what you mean!

Well it was either you or TJ. I don't care TBH, did me good getting off the internet.

From my house to my girlfriends grans in Scotland is 469.6 miles. It cost us pretty much dead on £100 to get there, £20 cheaper than the diesel. The only reason I can think is the petrol has cruise control, the diesel didn't, therefore more accelerating and braking etc.

I'd love to know what the chance of a DMF, DPF or injector failure is inside say 100 or 150k miles...

Very likely on a diesel because the increased torque kills DMF's.

Posted 6 months ago #
weeksy - Member

I'd love to know what the chance of a DMF, DPF or injector failure is inside say 100 or 150k miles...

There's a section on Talkford.com that has 3X the number of posts than any of the other sections.... "MK3 diesel techincal section"

There's a reason for that.

Posted 6 months ago #
vertical climber - Member

so do we all buy petrol just in case something goes wrong?? most parts are electronic now on all cars so jsut as much chance of going wrong ie fly by wire throttle, air flow control, injectors-controls etc etc

defo use quality diesel not supermarket stuff on modern ones though

Posted 6 months ago #
TandemJeremy - Member

flow - Member

I will get you banned? I've never reported anyone, if that's what you mean!

Well it was either you or TJ. I don't care TBH, did me good getting off the internet.

I did not report you.

Posted 6 months ago #
tonyg2003 - Member

From my house to my girlfriends grans in Scotland is 469.6 miles. It cost us pretty much dead on £100 to get there, £20 cheaper than the diesel
£100 is give or take 16 gallons and 469miles in 16 gallons is 28-29mpg. I think your sums are wrong somewhere! My 3.0 tdi does +40mpg even more if you stuck is a 70mph with the cruise on.

Posted 6 months ago #
flow - Member

£100 is give or take 16 gallons and 469miles in 16 gallons is 28-29mpg. I think your sums are wrong somewhere! My 3.0 tdi does +40mpg even more if you stuck is a 70mph with the cruise on.

There and back sorry

Posted 6 months ago #
molgrips - Member

Very likely on a diesel because the increased torque kills DMF's.

Sceptical. The DMF is there because of the higher torque. Are you saying that it is very the DMF fails on every car?

Posted 6 months ago #
cozz - Member

you are right, people have been lead to think diesels are soo much cheaper and they often are not

a mate recently had a MINT '03 mondeo 2l petrol he was selling for £800 - very cheap tidy respectable looking car for little cash - years worth of life left in it

even bigger price difference in 4x4's

ive had 2 jeep with 4.0l engines and converted them to LPG when i was doing 25k a year, the conversion cost paid for itself after 7 months !

as always the people who can benefit from this situation are people that do small mileages

Posted 6 months ago #
flow - Member

Sceptical. The DMF is there because of the higher torque. Are you saying that it is very the DMF fails on every car?

Why do you have to question everything anyone ever says?

New petrols have DMF's too, compared to diesels the amount of failures are extremely small.

Posted 6 months ago #
mboy - Member

Approval has nothing to do with it, I was just pointing out that there could be something wrong with the car or the driving style. And to add a bit of balance. You've got a V6 4WD car and are banging on about poor diesel mileage. Well the problem isn't diesel, it's apparently 4WD V6s, which is what I was trying to say.

Re-read what I originally wrote... I wasn't complaining about my MPG at all, I happen to think that 36ish average for my particular car is pretty good considered. I'm not unimpressed by the economy, it's the perceived cost of running a diesel vs running a petrol that's the issue.

This is all why i bought a Mondeo petrol recently.
£2000 got me a decent spec 1.8 petrol with 31,000 on the clocks... lol. Yes really.

Good find, and agreed... 1.8 Mondeo will do 40mpg on the motorway anyway (I've done a good few miles in numerous Mondeos and Focus' in my old job), the diesel will do about 47-48 on the same journey but will cost an arm and a leg to keep running! And for £2k the same car in diesel would have done 131,000 miles...

pre-posh DMF blah blah diesels are the way to go. we run a 1.4 & 1.6tdci fiestas
£30 quid tax a year 55+mpg, service them myself.

Still got a ridiculously expensive fuel pump and turbo to fail though! I know what you mean in principle though, buy and sell at the right time (like I did with my old Golf Mk3 TDi) you can do well out of the money saving on fuel, but buy one that might need a new turbo or fuel pump any time you're planning on owning it for, and you'll wish you'd bought a petrol!

It's ironic that the 2 cheapest cars (all costs included) that I've owned have been a Mk3 Golf Tdi that averaged 52mpg, and a BMW 540i that averaged 24mpg. The Golf cos at the time fuel was less than 10p a mile for it, and in 30,000 miles it only needed 2 wheel bearings and 2 shocks, and I sold it for £150 more than I paid for it. The BMW cos though it was expensive on fuel (21p a mile when I owned it, would be closer to 30p now), but again I made a profit on it, and I made a killing buying and selling 2nd hand parts for it.

Anyway, just found another Mk3 Golf TDi for sale in good condition and still low milage, so all is not lost yet. And it's a car I know well, and am happy to do most of the servicing on myself (and it's also a diesel that exceeds its quoted MPG!). Fingers crossed its as good as he said it was on the phone.

Posted 6 months ago #