Originally Posted By: edyvw
Originally Posted By: weasley
Originally Posted By: edyvw
Originally Posted By: loneryder
I'm assuming that my DPF will have more regens with a higher ash content but how much more really? If I have less oil fumes in the crankcase, won't there be less going thru the intake and exhaust?
It will, and longevity will decrease. Regeneration does not get rid of ash completely. DPF has life expectancy, and highr ash content (among other things) will shorten it.
I would tick to MB 229.51 strictly. I make sure when I buy oils that besides BMW LL-04, oil has MB 299.51 due to MB's deposit and NOACK requirements.
Regen does not get rid of ash
at all. The regen process overheats the DPF and burns away the
soot, which is particulate matter created by the incomplete burning of the fuel (the smoke that diesels make) - this soot is largely carbon and will therefore burn. The
ash from burning the engine oil is mostly metal oxides (from elements like calcium, magnesium, zinc and any other metals in the additives) - these will not burn away in the regen - they are staying there. Over time they accumulate and will eventually block the DPF permanently. This is why lower ash oils are specified, to reduce the ash build-up in the DPF, ideally to a level that means the DPF life will outlive the car (or, at least, outlive the first owner
)
Of course the amount of ash depends also on how much oil the engine burns, as well as what elements are in it. However, given the same oil consumption rate and process, a lower ash oil will always put less ash in the DPF than a full-ash one. If the DPF gets more ash-loaded then it will regen more often, trying (and failing) to clear it out - the regen process puts more fuel through the engine, potentially leading to higher fuel consumption, higher fuel dilution, bore washing and so on.
Regen burns soot and ash since ash regularly ends in DPF due to NOACK. Of course, regen will not be able to get rid of ash as good as soot, but there is constant pollution of DPF by ash due to regular oil evaporation loss. Lower the NOACK, better for DPF.
Of course, if car burns oil due to some failure like oil piston rings or valve stems, well that is different thing.
Also, city vs. HWY driving plays big role in DPF longevity.
What you guys are talking about is protecting the DPF. I want to protect my engine like the article says. My engine doesn't use any oil on a 5k oic. When I went 9k, it used about a third of a qt. When I drive it, I go usually over 50 miles mostly hwy driving. Doesn't a 15-40 oil have a lower NOACK than these 5-30's? Wouldn't there be less oil fumes to blow thru the turbo and burn downstream?