I think the rating is related to fuel that has been formulated for winter use, not the actual fuel temperature. To prevent gelling components are added to the fuel that lower the BTU rating of the fuel and thus the HP available to be extracted from it. Though, I can see by the last line of your post how there could be confusion.
Bob DuPuy Parrish, FL I was just looking at the specs for some new small marine diesels, from Yanmar. I noticed that they list two different horsepower ratings for different fuel temperature. For example, the engine I was looking at produces 20 HP with the fuel temp at 25 centigrade and 22 HP with the fuel temp at 40 centigrade. RPM etc are all equal. This is listed as "temperature at the inlet of the fuel injection pump."
