I have noticed that I get different mileage depending on where I get my diesel fuel. Am I crazy or is anyone else experiencing the same thing? Also I have seen people talking about summer and winter fuel as well as cetane ratings. Does one have anything to do with the other? I know these may seem to be basic questions but this is my first diesel and this web sight has been very informative.

 

I have found that a higher Cetane rating will provide better MPG, and a little better performance.
I always add Stanadyne PF when filling up, I add a little less when I can find high Cetane fuel.

Cetane number
NOUN: The performance rating of a diesel fuel, corresponding to the percentage of cetane in a cetane-methylnaphthalene mixture with the same ignition performance. A higher cetane number indicates greater fuel efficiency. Also called cetane rating.

 

Is 42 considered a high or low cetane rating. My local Hess dealer is 42.

 

From what I have seen around here, 42 is about average. The minimum cetane that can be dispensed by law is 40. Most stations advertising "premium" diesel will be a minimum of 45 cetane. I run whatever is the cheapest in my area. The higher cetane stuff usually gives me slightly better mileage, but really no huge gains.