Through comparing a few ROMs recently I have noticed some significant changes regarding oil dilution.
So far it seems, this is about newer Euro 6 diesel ECU firmware only, meaning MY 2015+. Apparently, firmware containing modifications were created in May 2017, probably published since 2017-07.
The oil dilution ratio threshold to trigger DTC P1468 Oil Dilution is now 15 % instead of 10 %.
A couple of tables have been adjusted, for example “oil dilution evaporation” is now defined up to 15 % and a few DPF regeneration behaviour tweaks.
Also, the relationship between log items “Distance To Oil Change [km]” and “Oil Dilution Ratio [%]” is not linear anymore, rather nonlinear in fact.
Both graphs were created out of 2015/2016/2017 Outback Diesel CVT ROM data:
JB4K104B, ROM date 2017-05:
Older Euro 6 CID
JB4K102B, ROM date 2016-10, and probably still applicable to all Euro 4/5 models:
I will update related pages in the near future.
For now, if you are affected, don’t use my custom “Oil Dilution 2” log item anymore.
If you like, you can use this simple formula instead, but it is only valid between 0 % and 8 %:
OilDilutionRatio3[%](DistanceToOilChange[km]) = 60-DistanceToOilChange/250
Since diagnostic item “Distance to Oil Change” is scaled in [100 km], above formula provides oil dilution in 0.4 % steps. Accuracy has become worse but is still better than standard log item “Oil Dilution Ratio” which only provides integer resolution. Not sure if logging apps such as Torque can handle table lookup or piece-wise functions.