If fuel can 'burn off' from oil, why does oil still smell like gas?...

[Klutch9]

...Specifically on vehicles that get driven at operating temp for a long time. My Explorer 2.3L GTDI is a good example. I typically drive quite a bit for work, at least two 25/30 minute drives per day to/from service calls, with some shorter drives in between. I also fairly often do longer highway drives where the vehicle is at operating temp for a long time. Yet, the oil always smells like gas. I'd think that since the engine spends a good amount of time with the oil hot, this wouldn't be that much of an issue. But I'm guessing that DI, especially GTDI, dilutes enough that the gas never really goes away fully?

 

[fdcg27]

My understanding of this is that the oil and the fuel are cosolvent, so the oil fuel becomes a part of the oil, unlike water, so while the lighter fractions of the oil might boil off a significant amount of fuel remains in the oil.

 

[4WD]

Would it need much benzene to retain the odor?

 

[rijndael]

I found this post helpful. https://bobistheoilguy.com/forums/t...temperature-heat-burn-off.259892/post-4217584

In short, just because some of it vaporizes/burns off at normal oil temps, it doesn't mean that it all burns off.

 

[KrisZ]

Simple, gasoline and oil are soluble. Water and gas/oil are not soluble.

And nothing is “burning off” in motor oil. Instead various lighter compounds are vaporized, leaving the heavier ones behind. Water gets vaporized too.