Fuel Dilution of Engine Oil

My driving is mostly short trips, 10 miles or less, I usually start and go very seldom any warm up. I take samples hot and am getting no lights or codes. My mpg decline happened about the time I noticed the dilution, decline and dilution have been consistant. Maintenance has been Amsoil 5W30 and filter every 5-6000 miles after 5000 break in with Dino oil. ECM and display were replaced after dilution was noted. Analysis shows no soot or combustion by-products. Until problem was noted analysis consistantly showed <.1% fuel.

I am the first and only owner of the car and my style has not changed since I have owned it.

Thanks for your time. Any and all ideas welcome.

 

Not sure where to go wrt diagnostics at this point

 

Back to basics: how about a cylinder leakdown test? Maybe piston rings on one piston are not forming a good seal with the cylinder, resulting in an excess amount of HC getting into the crankcase.

 

"wrt" "MAF" "CEL" ?

 

wrt - with respect to

MAF - Mass Air Flow sensor

CEL - Check Engine Light

 

Thanks, I was wondering how to check that.

 

A couple of general comments on fuel dilution. Many Prius owners do have fuel dilution, but do not realize it. Even those who have their oil analyzed may have fuel dilution when their analysis indicates that they do not. Blackstone does not use GC to determine fuel dilution. They have a chart that correlates flash point with fuel dilution and the test is not very sensitive. If you suspect fuel dilution is a problem and would like to address it I would recommend Dyson Analysis.

Also note that for Blackstone <0.5 % for Fuel dilution is lower than TR which corresponds to more than 0.5 and less than 1 %. Terry Dyson recommends Renewable Lubricants Inc. for cars with fuel dilution issues. It has worked well for my 2004 Prius. A final comment on fuel dilution is that it may cause problems which are not seen in an oil analysis such as excessive varnish buildup in the valve train.

I agree with Richard that 5000 mile oil changes are a good idea and using a good full synthetic oil may help to mitigate any problems.

There is more information on my experiences with fuel dilution in the following thread

http://priuschat.com/forums/gen-ii-...002-miles-mobil-1-0w20-used-oil-analysis.html

 

Another option is to use a test lab that primarily tests commercial engine oils. For heavy duty diesel engines used in mining, road transport, stationary power generation, construction, marine, etc, fuel dilution is of great concern

Those test labs, like Toromont Caterpillar, are pretty careful about how they test for fuel dilution

 

Since i changed from very low loading (to achieve MPG) to pulse and glide, I noticed a significant change in gasoline smell on the dipstick. Not a tech measurement, but gasoline smell did bother me at every oil level check.
Since then, normal motor oil smell with no gasoline detectable.
Not sure if engine loading affected oil temps or something else...
One person's observation.