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Matt, Mechanical Engineer
Category: Subaru
Satisfied Customers: 22747
Experience:  BEng hons Mech engineering, in auto industry 22 years
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What is the reason diesel fuel gets into oil of my 2011

Customer Question

what is the reason diesel fuel gets into oil of my 2011 Forester Navplus.
The DPF warning light flashes every 3 to 4 weeks but my mechanic says no fault logged by diagnostic system. He suggests that injectors may be "dribbling" and unburnt fuel is entering via pistons. Is this possible?
Submitted: 8 months ago.
Category: Subaru
Expert:  Nicola-mod replied 8 months ago.
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Expert:  Matt replied 8 months ago.


if you're getting diesel into the oil then yes the only source will be fuel leaking past the injector seals , so they are 'dribbling' and this then runs past the piston rings into the sump, its not uncommon

So its worth considering adding a bottle of injector cleaner into the tank as a clogged injector nozzle will reduce power and give poor combustion - the next stage on from this is to remove all the injectors and have them ultrasonically cleaned and flow checked