Buying High Mileage (100k+) Petrol vs Diesel

[arouse101]

Given the same mileage, generally speaking would it not make sense to buy a high mileage petrol car when you consider the additional major repairs that eventually need to be done on a diesel at a high mileage (I'm thinking of DPF/Turbo replacement) - repairs which a petrol car would not need.

I know that petrol cars in general have their fair share of maintenance costs and repairs which can be costly as well, but from what I understand a petrol would require less money spent on major servicing compared to a diesel. Is this true?

[liner33]

The higher servicing costs on diesels is a myth imo

DPF replacements do in most cases come along once in the life of a car

A 100k diesel engine with have less mechanical wear than a petrol by virtue of the fact it will have covered less revolutions.

But the biggest costs on older diesels can faults on the fuel system , ie injector blocks, injectors

[EuroFighter]

I would echo what you have said. I too would be wary when buying a 100k+ diesel vehicle purely because turbos/dpfs could be buggered.

You just don't know how the previous owner has treated the car. For example ragging the car and not allowing the turbo to cool down... My Leon was starved of oil which caused the turbo to fail (previous owners fault)....I got rid of the car because even with a new turbo (garage footed the bill) the car still let out blue smoke and the engine felt fckd. The Leon only had 60k on the clock!

Petrol engines all the way for me if buying used over 100k.

Edited by EuroFighter on Thursday 2nd October 10:23

[xxChrisxx]

EuroFighter said:

I would echo what you have said. I too would be wary when buying a 100k+ diesel vehicle purely because turbos/dpfs could be buggered.

I'd rather have a 5 year old diesel that's done 150k miles than a 5 year old diesel that's done 25k.
It's short journeys that fks DPFs and turbos. Doing what they were intended to do, with is plod endlessly on motorways, and they are fine.

The more cars I look at and drive, the less relevance I give to mileage. Why is 6 figures on the clock such a panic inducing number? It makes little sense to cut out a huge portion of the market on an arbitrary number on a trivial criterion.

Each car should be weighed up individually on it's merits and faults vs it's cost.

Edited by xxChrisxx on Thursday 2nd October 11:04

[liner33]

My mate has a 535d does a lot of miles each year travelling around the UK , at 135,000 the dpf failed , lots of people seem to think they will be fine if you do longer trips but they arent a lifetime fit they need replacing since they fill with ash. BMW reckoned he had done very well as they usually fail earlier, estimate was £1800+ vat to replace

[Harji]

Never had a problem taking a petrol Subaru Legacy Estate bought at 97K and a diesel 320d tourer bought at 74 K, both taken past 100K miles and sold at 125K and 110K respectively.

Both had usual consumable changes, but with the Legacy I never had any worries, but the diesel always put a thought in my head, maybe paranoia but I do think ppl get rid of diesels around the 100K mark because of worries about DPF's and injectors and so on, whether it's fact or myth doesn't seem to matter.

[mrnvh]

I can't vouch for high mileage diesel, but I drive a 2004 E46 320i touring with 162k miles on the clock. Its ex masterlease and averaged around 14k miles per year before I bought it.

Since owning it early this year I've replaced the following;
- Front suspension bushes, common wear item
- Front drop links, again, common wear item
- Radiator + Expansion tank - Radiator was bowing at the top + bottom with a tiny leak, tank was rock solid but to replace one you take the other off anyway.
- Rocker cover gasket - common E46 issue
- Accessory belt replaced

Never drinks oil, bang on 28mpg even with enthusiastic + town driving. Zero rattles and squeaks. Could do another 100k easily, the M54 engine is bulletproof from all accounts. The most expensive part being the radiator + expansion tank which was around £150 all in as I replaced them both myself.

[arouse101]

liner33 said:

The higher servicing costs on diesels is a myth imo

DPF replacements do in most cases come along once in the life of a car

A 100k diesel engine with have less mechanical wear than a petrol by virtue of the fact it will have covered less revolutions.

But the biggest costs on older diesels can faults on the fuel system , ie injector blocks, injectors

I can appreciate that a 100k diesel will have less wear than a petrol. That being said, comparing the repair cost of the extra wear on the petrol vs diesel fuel system failures cost I think you would probably find the diesel repairs end up costing more.

Even if the entire engine is replaced on the petrol - compare the cost of that vs cost of DPF/Injector/Turbo replacement and it probably will cost just as much.

Any arguemtns for this point?

[Dracoro]

liner33 said:

A 100k diesel engine with have less mechanical wear than a petrol by virtue of the fact it will have covered less revolutions.

It's not that simple, the force going through each revolution is different, different compression ratios, one has a spark to ignite and force piston, the other via compression etc.

Anyway, I have a 3.0 V6 in my car, I don't envision any problems for, say, 200k. If there is a problem, chances are it's due to bad luck. With many turbo'd cars it appears problems (of some form, major or minor) are to be expected.

I'd be as concerned, give or take, with a turbo diesel at 100k as with a turbo petrol at 100k. However, I would not be as concerned with a non-turbo'd car.

[thatdude]

liner33 said:

My mate has a 535d does a lot of miles each year travelling around the UK , at 135,000 the dpf failed , lots of people seem to think they will be fine if you do longer trips but they arent a lifetime fit they need replacing since they fill with ash. BMW reckoned he had done very well as they usually fail earlier, estimate was £1800+ vat to replace

If in that time that has been his only major cost outside routine servicing, I'd say that was pretty good going. I'd spend the £2000-odd and carry on using it.

I understand DPF's are designed for 100,000-ish miles of driving, but that is something i read on the itnernet, possibly on ehre, so its bound to be lies

As for higher servicing costs, I'm not sold on that either. You do everything the same on a diesel but no spark plugs. The oil for my wifes car (120D, pre-DPF) is more expensive, because it takes more of it, but even so we havnt noticed it being more costly than my petrol car. I think my petrol has cost more, because it has had to have a cambelt. Her's is timing chain, so it should be good for at the very, very , very least 150,000 miles anyway.

Edited by thatdude on Thursday 2nd October 13:48

Edited by thatdude on Thursday 2nd October 13:50

[gizlaroc]

liner33 said:

My mate has a 535d does a lot of miles each year travelling around the UK , at 135,000 the dpf failed , lots of people seem to think they will be fine if you do longer trips but they arent a lifetime fit they need replacing since they fill with ash. BMW reckoned he had done very well as they usually fail earlier, estimate was £1800+ vat to replace

Lots of DPFs fail because the thermostats are shot and therefore the DPF doesn't think the car is up to temperature and doesn't do a regen.

[PugwasHDJ80]

I replaced a 330d with a Focus ST170

Both started on 90k miles.

Their was a 12mpg difference in economy on a long term basis (29mpg v 41mpg)

The bmw cost me £6,000 more in repair costs

6x injectors at £180 each,
1x turbo at 120k miles (despite having a turbo timer), £2,200 fitted
1x DPF (which I bodged) but would now cost well over £1500
new auto box £2800

The ST170 cost me a 50p resistor and a £400 Dual mass fliywheel

[ModernAndy]

To be honest, I don't think it makes much difference either way. Things like DPF's etc. are always a risk because the further you go down the road of more and more kit, the more chance there is of something breaking. You'd hope the extra mpg would make up for these sorts of repair costs if they do happen. On the other hand, you're more likely to have some things like head gasket failure in a petrol engine.

Most cars cost money in things like renewing steering and suspension components, welding, wheel bearings and consumables in my experience.

My current banger which I'm turning into a winter hack once the temperature plummets a bit lower is a 51 plate Octavia estate with the 1.9 110 TDi and 221k on the clock. It's still solid and apart from a slightly dodgy fuel guage, very reliable (plus very cheap to run).

Overall though, if it's a car for fun/performance, I'd always go for petrol anyway.

[ShaunTheSheep]

If you visit a scrappies and there's a nice looking car, a car that's clearly not old / knackered enough to belong there.

It's a diesel. And noone can fix it.

[arouse101]

PugwasHDJ80 said:

I replaced a 330d with a Focus ST170

Both started on 90k miles.

Their was a 12mpg difference in economy on a long term basis (29mpg v 41mpg)

The bmw cost me £6,000 more in repair costs

6x injectors at £180 each,
1x turbo at 120k miles (despite having a turbo timer), £2,200 fitted
1x DPF (which I bodged) but would now cost well over £1500
new auto box £2800

The ST170 cost me a 50p resistor and a £400 Dual mass fliywheel

That's exactly my point, those extra costs for the Diesel exclusive repairs really do add up.

I would still say your comparison is a bit exaggerated that/or you got very lucky with your Ford Focus to only replace a flywheel.

[arouse101]

ModernAndy said:

On the other hand, you're more likely to have some things like head gasket failure in a petrol engine.

Head Gaskets don't really cost much more than ~£100 to replace (largely depending on car of course) which in comparison to diesel repairs is nothing.

[ModernAndy]

arouse101 said:

ModernAndy said:

On the other hand, you're more likely to have some things like head gasket failure in a petrol engine.

Head Gaskets don't really cost much more than ~£100 to replace (largely depending on car of course) which in comparison to diesel repairs is nothing.

I don't just mean head gaskets although I will admit the cost of repairs on a petrol are still likely to be lower. I'm just trying to say it's not a case of diesel cars being a devil for parts while petrol cars are angels.

[arouse101]

ModernAndy said:

I don't just mean head gaskets although I will admit the cost of repairs on a petrol are still likely to be lower..

Of course, but what kind of other major mechanical issues for petrol exclusive cars are there that you could think of?

[mike-r]

I maintain the cheapest engine you can run over its lifetime is a manual box mated to a chain driven inline or V6.

[ModernAndy]

arouse101 said:

ModernAndy said:

I don't just mean head gaskets although I will admit the cost of repairs on a petrol are still likely to be lower..

Of course, but what kind of other major mechanical issues for petrol exclusive cars are there that you could think of?

IME; piston rings, anything that damages spark plugs, coil packs and other (yes, I know, less expensive) things like that