[Quacker]

Volvo has a very close coupled DPF that is very efficient, because little heat is lost between the turbo's and it. Therefore most regenerations are probably passive and don't require much fuel to start a regen. I suspect because it is so efficient that they get away with just injecting some extra fuel in late combustion to the cylinder in order to raise the exhaust temperature. Some brands with more remote DPF use an extra fuel injector in front of it to inject fuel directly to ignite in front of the DPF, but that is not needed on the Volvo design.

The problems with fuel dilution occur when the DPF cannot attain sufficient temperature to regenerate. Not even enough with the supplementary fuel through the engine. What happens then is that the system makes multiple unsuccessful attempts and the fuel runs down the cylinder walls and past the piston rings into the sump.

There may be a couple of reasons why the system will not work as it should. First is that the car is not driven for sufficient distances and/or worked hard enough. It would help if the car was driven some 20 miles minimum at least once every 100 miles or so and particularly at a reasonable speed and load. Using Sport mode might help here. In general, lightly driven cars with automatic transmission [which keeps revs very low] which potter around on short and urban journeys are very prone to this. Diesel engines are not recommended for pottering around doing short journeys.

Secondly there may be a mechanical problem such as a leaky injector nozzle. It is vital that such an issue is diagnosed and remedied quickly, before serious damage to the pistons and bearings is done.