Anyone know what the difference in Cetane ratings are? For example, I pull into the Exxon station, Cetane rating is 40. I go to Amoco, theirs is 47. Is this similiar to using regular vs premium in a car? I can't say there is a noticable performance difference, but I get the 47 Cetane every chance I can!!

Steve=new to the board

 

Cetane ratings is roughly comparable to octane ratings for gasoline. It's a measure of the fuel's ignition and BTU characteristics.

The 47 should give you better mileage and quicker starts than the 40.

 

Octane is a rating of the fuel's ability to RESIST ignition.

Cetane is a rating of the fuel's ability to ignite.

In either case, higher is generally better.

Octane is almost always a result of the additive package. Tetraethyl lead in olden days gas. The more lead, the higher the octane.

Cetane is determined more on the cetane value of the base fuel, which varies from barrel to barrel. That is why there is more variability in cetane ratings. Diesel fuel producers only guarantee a fairly low number (must be at least 40 in the U.S.) because they don't know for sure what they will get out of the next barrel.

Some producers are more selective in their base oils, and are willing to step up to the plate and spec out a higher number. Amoco sell a "Premium Diesel" which they claim has a minimum cetane rating of 50.

The higher, the better, although many people do not notice any dfference.

You are better off buying really fresh 40 than old 50. Diesel loves to collect water and dirt the more it sits around.