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Here are some excerpts from the owners manual of my 2005. If available in your area, a high cetane “premium” diesel fuel may offer improved cold-starting and warm-up performance. Number 2 Diesel Fuel Specifications Cetane Number - 40 min. (ASTM D613) Number 1 Diesel Fuel Specifications Cetane Number - 40 min. (ASTM D613) I didn't see it in the manual, but I believe 45 is the min for <32°F Cetane is similar to Octane in that there are design specs for a certain number, which is why 30 may have more BTU's but doesn't operate as well based on design specs.

I've got friends up in Sturgeon Bay, WI. Quite a few extended family members of theirs have worked in the ship building industry. A lot of the really big boats with the monster diesels in them have to "pre-heat" the fuel to make it thin enough to pump and inject. They said it's almost like "TAR" until it's heated. Wonder what the cetane level is for that goo??!!!

Cetane

Low Cetane <---------------------------------------------------> High Cetane

Octane

High Octane <----------------------------------------------------> Low Octane

Low cetane diesel burn slowly and difficult to ignite but contains the most BTU's simular to high octane gasoline.

High cetane fuel burns very rapidly and easy to ignite but contains lower amount of BTU's simular to low octane gasoline.

Cetane

Low Cetane <---------------------------------------------------> High Cetane

Octane

High Octane <----------------------------------------------------> Low Octane

Low cetane diesel burn slowly and difficult to ignite but contains the most BTU's simular to high octane gasoline.

High cetane fuel burns very rapidly and easy to ignite but contains lower amount of BTU's simular to low octane gasoline.

I believe I know what your trying to say, with your example above, but I'm not sure it's correct. As I understand it there is very little difference BTU wise between Regular and Super. Just that the Supers higher octane rating allows you to produce more power from a high compression engine by allowing more timing before pre-detonation.

E85 for example is around 105 Octane but only 75-80k BTU depending on purity.

Poke here for a discussion on the topic http://forum.onlineconversion.com/showthread.php?t=233

I believe I know what your trying to say, with your example above, but I'm not sure it's correct. As I understand it there is very little difference BTU wise between Regular and Super. Just that the Supers higher octane rating allows you to produce more power from a high compression engine by allowing more timing before pre-detonation. E85 for example is around 105 Octane but only 75-80k BTU depending on purity. Poke here for a discussion on the topic http://forum.onlineconversion.com/showthread.php?t=233

I believe this to be correct. Back in the days of leaded gasoline; the lead was added to increase the "octane rating" of the fuel. Nowadays other products are added to increase the "octane rating" of gasoline............ethanol comes to mind!!!! The higher octane rating allowed for a higher compression ratio in the cylinders because it delayed pre-ignition enough to allow the spark plugs to ignite the air/fuel mixture. I don't think there was that much difference of BTU's in the fuel based on the octane rating. It is only a rating also. If you look at the gasoline pumps; it says 87 Octane in big numbers. Below that, in smaller print, it says something like R+N/2 method. There are 2 methods or equations to figuring the octane rating. They just take the average of the 2 methods.