If fuel dilution occurs - does the Oil temp increase ?

Thinner oil = hotter oil...
 

all things being equal.

Dave be correct. Less thermal mass = higher temperature
 

You can actually watch over time as the oil temperature increases as it dilutes. Then listen to your engine thank you when you put new oil in and the temperature goes down.

Also increased friction=increased temp=increased wear. All bad.

So temps < 200 at cruising speed = little significant fuel dilution
 

Thought this would drive rirs4 crazy :)

I don't think he got past the basic formula...yes, things thin out as they heat...
 

even the atmosphere.

< 200 F cruising = = very good
 

As long as it holds over the life of the oil. What often happens is oil being diluted at cold start and short driving cycles, and never having the chance to recover.

This winter we've seen a lot of high dilution and low flashpoint. It may be a consequence of winter driving. It also may be that these cars have a few more miles on them and are over the "magic" 5K limit.

One possibility I've hypothesized is that the "magic" 5k ECU remap increases the amount of dilution. So far, the record bears this out. Dilution is higher, and flashpoint is lower, for oil that was placed in service after 5000 miles. But this also corresponds to the winter months, so the increase might just be due to longer warmup cycles, too. In that case, I expect that fuel dilution would be lower in warm climates, and over the summer. Unfortunately, none of the southern contingent is rich enough to afford a $50 oil analysis. So we don't have data from the warmer winter climates. Our data comes from Washington, Michigan, Colorado and New England.