Diesel Car 26k in 7 years

sparky55

Hi,
Im looking for some advice.
Im in the market for a BMW 20d X1 auto.
Alot of deals I’m finding are cheaper with diesel, but from past experience with diesel cars I’ve had dpf issues and cost me a fair price (both previous cars done over 100k).

I’ve seen a deal I like but it’s 2018 plate and only done 26k on the clock, is this a concern as I’m aware you need to try and do high mileage/moterway runs often to reach a temperature to burn the clog away.

Any advice would be appreciated.

ButterCheese

The DPFs tend only to create an issue if drivers ignore the warning light/DPF light which tells you it is nearing capacity.  My old car (a 2014 VW Passat) would throw this up if you had only done short trips for a week or so without any long runs.  It actually said on the dash "drive at least 30mph for 20 minutes" or something similar. 

It is an extra hassle to go for a drive ebery time this happens, but if you only do short trips then I would question whether a large diesel is right for you.  I took these DPF-clearing drives to be part and parcel of good maintenance; sometimes I'd have to go 15 minutes before the light cleared, other times it was 30 minutes.  but that was a week or two of just school runs so pretty much to be expected.

The only time they get fully clogged is if the sensor fails (i.e. you get no warning light on the dash when the DPF is full), or you ignore it for too long, or if the heating mechanism fails etc which I would have thought would throw up another code anyway.  The Adblue system can also fail and cause problems, but I'm not sure how widespread this is.

Just to add, I did an 18 hour round trip in mine with very few stops, and thought this would give it a good clean out and maybe prevent it getting clogged so quickly.  But it behaved just the same as it did before the long trip.  So I don't think there's much you can do besides maybe using a DPF cleaner additive in your tank (which some say is snake oil but others swear by it), and always clearing the DPF as soon as the light pops up

sparky55

Hi,
thanks for the reply.

so I guess there’s no way of knowing if the dpf in the motor I’m looking at will be ready to break.


i work offshore so for the next year before my partner passes her test it will be sat for 3 weeks at time in Aberdeen, it will get a blast from Dundee to Aberdeen and back each month but not sure if that will be enough to maintain the dpf system 

35har1old

ButterCheese said:

The DPFs tend only to create an issue if drivers ignore the warning light/DPF light which tells you it is nearing capacity.  My old car (a 2014 VW Passat) would throw this up if you had only done short trips for a week or so without any long runs.  It actually said on the dash "drive at least 30mph for 20 minutes" or something similar. 

It is an extra hassle to go for a drive ebery time this happens, but if you only do short trips then I would question whether a large diesel is right for you.  I took these DPF-clearing drives to be part and parcel of good maintenance; sometimes I'd have to go 15 minutes before the light cleared, other times it was 30 minutes.  but that was a week or two of just school runs so pretty much to be expected.

The only time they get fully clogged is if the sensor fails (i.e. you get no warning light on the dash when the DPF is full), or you ignore it for too long, or if the heating mechanism fails etc which I would have thought would throw up another code anyway.  The Adblue system can also fail and cause problems, but I'm not sure how widespread this is.

Just to add, I did an 18 hour round trip in mine with very few stops, and thought this would give it a good clean out and maybe prevent it getting clogged so quickly.  But it behaved just the same as it did before the long trip.  So I don't think there's much you can do besides maybe using a DPF cleaner additive in your tank (which some say is snake oil but others swear by it), and always clearing the DPF as soon as the light pops up

Driven a Mazda 6 for 15 years now with 51500 on the clock never had DPF light on no ad blue system
VW Golf same age but with more miles on the clock DPF light on several times but car never was the same after the diesel recall fix 
Golf went into limp home mode on a long journey no ad blue system
No longer owned
Are parts readly available for BMW have heard parts for Mercedes difficult to obtain quickly

fwor

sparky55 said:

it will be sat for 3 weeks at time in Aberdeen, it will get a blast from Dundee to Aberdeen and back each month but not sure if that will be enough to maintain the dpf system 

Sitting there doing nothing won't harm the DPF at all. It's short journeys that will do the damage. The one thing that will kill the DPF on a diesel quickly is people using them just to do short school/shopping runs. Modern diesels are so efficient that they take 20 minutes or more driving to get up to working temp, and the DPF can't regen at all if all the journeys are less than that.

My 12 year old diesel van has only done ~48k miles, and it can sit for 4 months in the garage every winter, but it never does any journeys of less than about 30 miles - so the DPF is still fully functional.

Frozen_up_north

OP, do you really need a diesel? My Seat Leon, 1.5 turbo petrol (150 hp automatic) has just returned 58 mpg on a cross country run, according to the dashboard, shorter runs are typically 42 ish.
Given the higher cost of diesel and potential issues with DPF clogging, I gave up on diesel a couple of cars ago and don’t regret switching. My travel is no more than 20 miles most days, sometimes only 4 or 5 miles, with the odd run of 100+ miles perhaps 5 or 6 times a year.

Nasqueron

I have a diesel Mazda 3, do about 7000 miles a year, I do 2-3 short trips a week (supermarket and gym, 10-20 minutes) but the majority of my mileage is for a sport I do or social trips at the weekend when I do anything from 1-4 hours motorway each way. I accept I am not your typical driver but doing those long motorway drives regularly over the last 11 years has meant I never had any DPF issues despite the lower mileage

Goudy

It's not the low mileage as such, it's the length of trips.

The issue for most diesel cars with DPF's isn't one trip a week 100 miles each way.

It's the 5 minute trip here and the 5 minute trip back later in the day, over and over again, day after day.

The first trip profile has plenty of time to regen.
The second doesn't stand much of a chance to regen.

Soot is fuel that hasn't completely burnt.
Lots of cold starts cause the fuelling to be rich, so more soot is generated.

The DPF needs a fuel source and heat, 600c or more to burn the large particles of soot trapped in the filter to ash, which have far smaller particles that the filter can hold more of.
Short tripping won't generate the heat, so a regen cycle won't start and the filter clogs.

Also if it did start and you turn off the engine mid cycle, the fuel injected to burn the soot to ash can find it's way into the engine oil and dilute it.
This can cause all sorts of problems.

Modern petrol engines are fitted with particulate filters these days
They don't handle the amounts of soot as a diesel, but short tripping can cause similar issues.
Modern petrols also tend to generate lots of heat on the over run, so some particulate filters on petrols are actually passive, they just burn the soot to ash without injecting fuel in there.