[setlow]

Hi, long time lurker here!

I've been reading all these threads with interest as I have an 06 185 that has done 200k! I had all these problems with the DPF, limp mode, burning more oil that an old stove... lots of comments from various mechanics of fault being turbos, piston rings, seals etc…

Anyway, I was planning on getting rid of the car anyway soon so was looking for the cheapest possible fix to tide me over and just keep the car running for a few more months and my local indie power washed out the DPF and it's now almost like driving a new car!

The car was burning 0.5l, then 1l, then 2l per 1,000 miles, to the oil going from full to the oil level warning on the dash in a single tank of fuel! That’s when I gave up and decided I should try something before I scrap it as it’s not worth a new engine to me!

So the DPF was power washed out, with some cleaner and detergent or something (I didn't do it to know) and I’m back down to a burning a minimal amount (not yet managed to work out exactly as the consumption so far is too low to calculate, but I reckon it's easily below half a litre per 1,000). No limp mode, power is back up to something more reasonable and the MPG has gone from 24 to 31!

I won't confess to understand the exact details of a modern diesel engine, but I get the basic process, and I presume the exhaust being unable to breath is causing problems all the way back up the system right to the cylinders which then vent into the case and causing what others are referring too as oil being dragged out of the vent into the air intake (I don't know enough to understand exactly how this part is all linked to pass any comments – I didn’t even know the case vented to the intake, I thought it vented to the outside!).

Has this higher pressure damaged piston rings, caused cylinder wear, damage to the turbo seals and everything else? I'd guess so, but in terms of a simple fix I'd get your DPF cleaned or replaced, and personally I’d just get it power washed out as a cheap option.

I’ve seen comments that you can’t clean a DPF out by power hosing, and I’m sure the pro companies will do a great job and remove most of what’s in there. However, power hosing in my case has removed a lot and enough to make it run well, for now at least. Also – what came out was not soot, it was ash. While the DPF will remove soot as it burns it off in the regen cycles, ash cannot be burnt by its nature and I guess is inevitable that they’ll clog eventually. (ok I simplified here, you can kind of burn ash, but it'll eventually results in compounds that cannot be burnt, and what came out was white powder so it's probably calcium oxide, and other oxides formed from the things that make up oil.)

I guess with a DPF what the unknown was when they introduced them was how much ash does an engine produce, is it from the fuel, the additives, the oil, are some fuels better or do some contain too many impurities and are there things we can do in terms of maintenance to reduce the ash that is coming out? That said – on the next car I’ll probably watch the mpg more closely and when after 100k it starts to look like it’s creeping down I’ll probably send it off to be cleaned professionally as I think it’s likely to make a big difference and should be part of the maintenance schedule!

However, after 200k which must be around 30,000 litres of diesel burnt... maybe it shouldn't be a surprise that you've got half a kilo to a kilo of non burnable debris left!