Reducing oil dilution in priusII

The looks more like a coolant leak into the sump and not fuel. Condensation can cause some of that coloring but that is some sketchy looking fluids.

 

A lot of third gen OCC's are looking thus, especially through winter months. My engine coolant level reservoir level stays very steady. It did drop from full to low line (maybe 1/2"?) in about 50K km since new. I topped it up at that point, and now at around 75K it's about halfway between the marks. That seems fairly steady to me. Also, there was a different smell to that stuff, compared to engine oil, gas I think.

 

Well remember its a sealed system but expansion and contraction can happen and it may overflow a bit from the reservoir bottle but your radiator will be fine as long as there is fluid in the bottle and no leaks observed.
I did forget to mention the Heated Water Storage tank behind the bumper. It does have hot coolant at all times in the tank right after you shut the vehicle off, which it stores.

 

Your Prius has a problem and you just have a way to reduce oil dilution. I would think it would be a lot better to fix the problem and then see if the oil dilution is also stopped. It would help you and all the other people with the same problem to find a fix.

I have fixed other problems that were diagnosed based on fuel trim numbers (on other cars). And I have looked from Prius repair manual that fuel trims in the Prius work the way that they work on other cars, the way I’m describing.

You do not really understand how fuel trims work. They are just used to correct the injected fuel amount calculated from information from all other sensors. So richening the mixture for cold engine isn’t done with fuel trims.

This quote proves that you don’t really understand how fuel trims work.

Let’s say the air fuel ratio sensor is reporting that engine is running rich control unit will then LOWER the fuel trim numbers (short term fast and long term slower based on short term) to REDUCE the amount of fuel injected. If control unit already is redusing the amount of fuel injected by 30% with total fuel trim of -30% but air fuel ratio sensor is still reporting RICH you get a code for rich P0172

So NEGATIVE fuel trim -> REDUCED amount of fuel injected -> (if reduced a lot and still running rich) code for running RITCH.
And it of course works the other way as well.
POSITIVE fuel trim -> INCREASED amount of fuel injected -> (if increased a lot and still running lean) code for running LEAN.