"I don't do enough miles to justify buying a diesel"

"I don't do enough miles to justify buying a diesel"

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Discussion

rockandrollmark

Original Poster:

1,170 posts

200 months

Monday 27th October 2014
quotequote all
Excuse my ignorance on things, but why do folk say this? I'm looking to change my aging Golf with something a bit more grown up. With the pump cost of diesel coming down to not much more than petrol these days I'm thinking the replacement might end up being something like a PD engined A4 estate or similar, but then I keep on hearing people say the above. My daily commute is going to be barely anything (5 miles each way) but after having lived with a rather expensive to run Mercedes previously it'd be nice to have something which doesn't drink like a fish on longer drives. That said I don't want to end up buying something that doesn't suit my needs.

So why do people often advise against a diesel if you're not doing high miles? In my layman's understanding of things, 2x cars next to each other; same spec, age, miles and price I'd go for the oil burner if low running costs are high on the list. Can someone set me straight?

surveyor

16,676 posts

161 months

Monday 27th October 2014
quotequote all
Diesels can often drown themselves with ash if they've not been given a decent run.

Also car costs more (but is worth more), and fuel costs more so there is a calculation to be done.

Diesels also used to be more complicated, but I'm not so sure that this is the case with the modern 'eco' petrol car. They have the Turbo's etc now too.

Tyre Tread

10,006 posts

193 months

Monday 27th October 2014
quotequote all
Diesles aren't efficient until warmed up and they don't warm as quickly as petrols so fuel efficiency on lots of short runs will be little betrer than petrol.

The DPF issues are also a major consideration.

CarAbuser

623 posts

101 months

Monday 27th October 2014
quotequote all
rockandrollmark said:
With the pump cost of diesel coming down to not much more than petrol these days
The Shell I stopped at last night had petrol at 123.9 and diesel at 128.9. The gap seems to be the same as ever.

406highlander

182 posts

110 months

Monday 27th October 2014
quotequote all
My understanding of this may be flawed; I don't own or drive a diesel. But here goes:

Diesels (especially modern diesels) are fitted with particulate filters (part of the exhaust system, fitted between the exhaust manifold and the catalytic converter), in an effort to cut down on harmful carcinogenic (cancer-causing) emissions.

The filter will, over time, clog up - were it not for the regeneration process. This is usually an additive fluid system which is automatically added to the fuel supply so that it raises the exhaust temperature. The raised temperature causes the particulate filter to burn off the excess crap that accumulates there.

Unfortunately, the regeneration process is triggered by temperature. If the car doesn't get up to temperature, the regeneration process never takes place, and the car will choke and enter "limp home" mode - engine management light lit, call the AA/RAC/Green Flag/Whoever. £££.

If you don't drive big enough distances, your diesel car will clog up and die.

Petrol is better for shorter journeys because it warms up quicker. Particulate filters will eventually come to petrol engines by way of EU regulations - but when they do, petrol engines will reach running temperature more quickly than diesels, and the particulate filter regeneration will happen much more often.

Mr2Mike

20,143 posts

232 months

Monday 27th October 2014
quotequote all
1) Modern diesels are not suited for regular short journeys, especially anything with a DPF.
2) If you are doing low annual mileage, then the saving on fuel costs will be low anyway compared to an equivalent modern petrol engined car.

unpc

2,680 posts

190 months

Monday 27th October 2014
quotequote all
It's because driving a diesel is one of the most soulless experiences ever. They also take an age to warm up and until they are properly warm will not deliver the kind of mpg you are expecting with getting started on the dreaded DPF issue that will likely become a problem on such a short commute. For that kind of distance I'd cycle or bus it and keep something tasty for weekends. Quite why anyone would pick one over the equivalent petrol is beyond me, and I've got one.

ETA I doubt the PD engines ever had a DPF but they sound like cement mixers.

ecsrobin

14,499 posts

142 months

Monday 27th October 2014
quotequote all
My friend went from a newish BMW petrol to a slightly older BMW diesel (similar cost) to save money as diesels get better MPG. My 1.8 petrol civic destroys his MPG and as someone above has said unless it's a decent length journey it's not that economical as he soon found out when in fact after a year of motoring realised it had cost him more to run the diesel.

I think they're was an average sum of 12-15,000 miles before it was considered worthy of buying a diesel but I may just be getting confused and making that up.

cptsideways

13,295 posts

229 months

Monday 27th October 2014
quotequote all
Its not miles per year, but journey type thats important.

Diesels when cold are still way way more efficient than a petrol engine, bear in mind though with a derv you generally don't get any cabin heat worth talking about till 5-10 miles down the road, crap on a sub zero morning! Unless you have a Webasto equipped variant eg 530d/Audi A2 et al


In your budget things change quite a bit to the "new car" diesel reasoning

rockandrollmark

Original Poster:

1,170 posts

200 months

Monday 27th October 2014
quotequote all
Aye - all this talk of DPFs is why I'm thinking if I go diesel it'd be an old PD engined Audi (pre DPF). I wouldn't touch a modern diesel with a barge pole. Too many horror stories about blocked injectors, dual mass flywheels, particulate filters.

So take it for a run every now and then and give it a good boot to clear the crap out and it should stay good, but don't expect mega-economy on town runs?

Monty Python

4,793 posts

174 months

Monday 27th October 2014
quotequote all
For less than ~15000 miles a year, get a petrol.

1. No particulate filter to clog up
2. It will cost less (a diesel costs more to start with and the fuel economy savings will take years to claw back).
3. It will sound better
4. You don't need to wear gloves at the pump (diesel smells)



That's why I drive a diesel (although it does have a couple of redeeming feature - namely 6 cylinders and two turbochargers).

swisstoni

12,909 posts

256 months

Monday 27th October 2014
quotequote all
As the OP has only a 5 mile commute, and is keen not to spend a lot on fuel I'd be looking at the relative cold start fuel consumption.
I have no idea if there is a difference but if there is it could be a factor in the decision.

As a slightly extreme example, I used an XJ12 as a station car for a while. The sight of 7 mpg meant I bought a bike pretty soon.

spats

838 posts

132 months

Monday 27th October 2014
quotequote all
I would go for the PD 1.9tdi all day long. I drive 12 miles each way and the journey is mainly 50mph roads with traffic, and a little bit of 70mph with no traffic but a few roundabouts thrown in.

I average real world (not off the mpg screen) 42mpg+ in our old Golf and about the same in our A4, both with the 1.9tdi. Heating up doesnt take long and theres enough points during the trip to open the vanes on the turbo to stop them sticking. My last car was a petrol and I got 27mpg on the very same trip.

Stick with the 115-130bhp 1.9's and as long as the oil/cambelt/water pump is changed and its given a good blast it should be a good car.


trickywoo

9,884 posts

207 months

Monday 27th October 2014
quotequote all
There is a lot more to go wrong with a modern diesel and a single failure of a fuel pump, dual mass flywheel, turbo will wipe out any savings on fuel in a stroke. This applies to even high annual mileages.


SpeckledJim

28,264 posts

230 months

Monday 27th October 2014
quotequote all
A diesel will cost less to fuel, but more to maintain.

The modern electronic gubbins that makes them 'clean' and drivable is all fragile and hugely expensive, and sometimes goes wrong.

If the diesel is saving you £2000 a year in fuel then you can justify the odd £800 bill.

If it's only saving you £200 a year in fuel, it isn't going to be worth it.

(That said, modern turbo petrols are catching-up in terms of fragile electronic gubbins)

Poopipe

619 posts

121 months

Monday 27th October 2014
quotequote all


We have a 2.0hdi in our 2001 picasso that has for the last 4 years done stty town driving, stop start etc and hasnt had a single exhaust or fuel related issue and has consistently returned very respectable fuel economy.

I hear that the more modern engines with all the extra emissions related filters etc will explode in your face if you shut them off less than 3000 miles after you turn them on but this may just be internet scaremongering and bullst.

The miles per year argument makes sense if you're buying new/nearly new as the initial outlay is significant as is the difference in price between petrol and diseasel .

If you're looking at an 8 year old audi these numbers shrink very fast and you'd probably see a return on your diesel investment very quickly indeed even if you dont do mega miles so the argument falls flat on its face and diesel wins.

Expensive failures/maintenance are an issue for sure but a petrol car is perfectly capable of throwing up a repair that isnt worth doing by the time they're 7-8years old.

Basically buy a diesel if you want, I cant see how its any more risky than a used petrol.

I cant see why you'd run one by choice unless you were doing a lot of motorway work or towing things but thats me.

dme123

8,734 posts

166 months

Monday 27th October 2014
quotequote all
I think you can take all the discussion of reliabilty, short journeys etc out of the equation and just say "If you're only doing low mileage you will only save a tiny amount of money. Why put up with the driving compromises of a diesel to save (say) £250 a year?".

Efbe

9,251 posts

143 months

Monday 27th October 2014
quotequote all
rockandrollmark said:
Aye - all this talk of DPFs is why I'm thinking if I go diesel it'd be an old PD engined Audi (pre DPF). I wouldn't touch a modern diesel with a barge pole. Too many horror stories about blocked injectors, dual mass flywheels, particulate filters.

So take it for a run every now and then and give it a good boot to clear the crap out and it should stay good, but don't expect mega-economy on town runs?
as is particularly tyical on PH.

I assume you are ignoring 90% of the advice on here, and only reading what you want to read.

quite simply at 5 miles per commute; diesel is pointless.

no point explaning why as many others have already

BL Fanboy

337 posts

119 months

Monday 27th October 2014
quotequote all
All fair points about diesels certainly.

I had a 150bhp Astra Diesel and to be fair, even off boost it responded pretty well to the throttle and we're only talking very low revs - the turbo made its presence felt from about 1300 rpm onward.

Had an effortless whiff of throttle feeling on hills.

If you like the easy going, and midrange surge that a diesel gives then why not. You wont get a petrol that will give anything like that feeling without going up massively in size with resultant thirst.

I know that if I got (say) a MK3 2.0 Mondeo petrol it'd feel pretty limp next to the TDCI 130. (Reliability of that engine aside ha ha)

Just need to know the downsides and be realistic about the proposition of using a diesel low miles.

My money would be with a PD engine car, just a shame they are so darned expensive year for year. Maybe its because they are good that they seem to command a premium.

rockandrollmark

Original Poster:

1,170 posts

200 months

Monday 27th October 2014
quotequote all
Efbe said:
rockandrollmark said:
Aye - all this talk of DPFs is why I'm thinking if I go diesel it'd be an old PD engined Audi (pre DPF). I wouldn't touch a modern diesel with a barge pole. Too many horror stories about blocked injectors, dual mass flywheels, particulate filters.

So take it for a run every now and then and give it a good boot to clear the crap out and it should stay good, but don't expect mega-economy on town runs?
as is particularly tyical on PH.

I assume you are ignoring 90% of the advice on here, and only reading what you want to read.

quite simply at 5 miles per commute; diesel is pointless.

no point explaning why as many others have already
Heh - No, I'm all ears to the advice of others, but trying to split the truth from internet scaremongering. As with my earlier example I'm trying to split the difference between buying two identical cars (purchase price, miles and spec) but with different engines.

Whats coming out here is that I'd be unrealistic to expect 60mpg on a short run (I figured that would be the case) and if I get a modern-witchcraft diesel I should expect the potential of a big bill.