Running a diesel car with DPF on not many miles per journey/year?

JustAnotherSaver

Not a thread for the "a diesel car is only for those who do 500,000 miles per year" lot.

Also if you're doing say 20k per year and munching them motorway miles then also not really one for you.

Was talking to a guy who doesn't do a load of miles today and has just bought an A3 2.0 170bhp which has a DPF. Horror stories are pretty easy to find online. There's a queue of people ready to tell you your car will explode if you don't live on the motorway. What i'm looking for seems harder to find...

Do any of you own a diesel car with a DPF and you don't really do all that many miles yet your car is absolutely fine and you've had no issues regards the DPF at all (providing you've owned it for longer than 5 minutes of course)?

caprikid1

Our 2015 Passat had DPF issues due to COVID short school runs and no commuting . Now we are forced to drive it to keep it alive . Petrol Golf no issues obviously.

Scrapit

Warm it through enough and you'll not have problems. Do less miles than it takes to clog and you'll not have problems. Only do the sorts of milage that will clog it, eventually you will.

missile

JustAnotherSaver said:

Not a thread for the "a diesel car is only for those who do 500,000 miles per year" lot.

Also if you're doing say 20k per year and munching them motorway miles then also not really one for you.

Was talking to a guy who doesn't do a load of miles today and has just bought an A3 2.0 170bhp which has a DPF. Horror stories are pretty easy to find online. There's a queue of people ready to tell you your car will explode if you don't live on the motorway. What i'm looking for seems harder to find...

Do any of you own a diesel car with a DPF and you don't really do all that many miles yet your car is absolutely fine and you've had no issues regards the DPF at all (providing you've owned it for longer than 5 minutes of course)?

I have owned two Audi A3 2.0 TDI and had no trouble with DPF.
I currently own an Audi SQ5 3.0 TDI since 2013 and have no trouble with DPF.

noclaf

I think it's a lottery. A friend's A6 with what I believe to be the same engine had dpf and egr issues..the eventual bill was eye watering as two different indie's couldn't resolve it so it ended up with an Audi main dealer...but was out of warranty.
I have other friends who have diesels ( Audi and Volvo)..lots of short stop start journeys daily and no issues so far....absolutely no idea why it seems to impact some engines and not others even when it's the same model etc

I would of bought a diesel as prefer the torqueyness of the engines but the dpf/egr horror stories and the 'war on diesels' means I probably won't...I also do 5k per year so have no way to justify it! 

AdrianC

My mother had a 58-plate 207 1.6HDi for 11 years and about 60k. It had one hiccup, when the light came on and it reported low fuel pressure on the rail. The fault code was cleared, it was happy, and it never did it again.

neilmcl

I've had a BMW 120d for 4 years now and it's done very low mileage in that time, particularly over the past year. Not had any issues with the DPF. It's not the number of miles that count, it's how they are driven.

bartelbe

Why take the risk? For low miles just buy a petrol car.

Mickey666

neilmcl said:

I've had a BMW 120d for 4 years now and it's done very low mileage in that time, particularly over the past year. Not had any issues with the DPF. It's not the number of miles that count, it's how they are driven.

Agreed.
Before lockdown I did about 11-12k miles per year.  In 2020 I only did a little over 5k miles.  But living in the sticks my nearest town is a 25 mile round trip, so if I start the car at all it'll be 25 miles minimum.  Say 5 miles to properly warm up and the other 20 at full temperature, even with short stop.  Plus, most country roads are done at 50-60mph so it's a decent run.  97k miles, never even had the DPF regen light come on.

Goudy

You need to remember this DPF "regen" isn't a fresh start for the filter. The term is a bit misleading.
What actually happens is the filter traps the soot, which has quite large particules and then every so often the soot is burnt to ash, which has smaller particules so the filter can hold more.
Eventually, even if running conditions are perfect it will fill with ash, sooner or later.

Problems tend to arise when "short tripping" a diesel with a DPF because cold starts tend to be richer in fuel and therefore produce more soot, so the process of burning the soot  (regen) happens more often, filling the filter with ash quicker. 
More soot = more regen cycles = more ash.

Also the process of "regen" can cause further issues. 
To reach the required temp to burn the soot a small amount of extra fuel is injected post combustion (not on the Bang stroke but on the Exhaust stroke), so it's not burnt in the cylinders but passes through them into the filter where it's ignited to burn the soot.
Some of this post injected fuel does pass the piston rings and mix with the engine oil causing it to dilute a little.
Repeat this more often and the oil becomes compromised as it dilutes but will also starts to rise. 
If it rises too much it can find it's way back into the engine and run uncontrollable on it until it runs out and the engine goes bang!

Now if you throw in another complication and your short trips aren't allowing for these regens to fully complete as you're switching the engine off before it's finished, you're just accelerating both problems massively. 
The filter isn't burning the soot to ash so the filter clogs with larger particules soot and the regen process keeps trying to complete sending more post combustion injected fuel towards the filter but more if it is ending up in the engine oil.

Biggus_Dickus

bartelbe said:

Why take the risk? For low miles just buy a petrol car.

My son has a Vauxhall GTC 2.0 Sri CDTi Auto. Not long after he bought the car he changed job which meant his commute to work and back was drastically reduced to only 10miles, nearly all of which is dual carriageway.

His annual mileage is approx 6k/year. The DPF regen message comes on very occasionally and he just takes it on a short motorway journey at high revs/low gear. The regen completes in just a couple of minutes.

He’s had the car 4.5 years and it runs sweet as a nut. So far anyway.