|MadSci Network: Engineering|
You are not going to find an exact answer to this question because, like all refined products, diesel fuel varies in its properties from refinery to refinery, season to season, etc. One can, however, get a number that will probably be reasonably representative.
The densities of petroleum products are traditionally (especially in the U.S.) expressed as "API Gravity" The API Gravity is related to the specific gravity by the equation: API = (141.5/SPGR) - 131.5, where the specific gravity is the density relative to that of water and everything is measured at a temperature of 60 degrees F.
So what is a typical API gravity for diesel fuel? The classic book "Petroleum Refinery Engineering" by W.L. Nelson (4th ed., McGraw-Hill, 1958) gives numbers ranging from about 25 to 40 (with "Grade 1-D" around 40 and "Grade 2-D" around 35). In a Web search using the keywords "diesel" and "API gravity" I found a couple of sites with specs for #2 diesel fuel; these had minimum values of 26 and 30 API gravity. So a reasonable guess would be that typical #2 diesel fuel would have an API gravity of about 35; I'll let you plug that into the above formula to get the specific gravity.
If you want more details or a more precise number for a specific fuel, I would encourage you to post your question to the Usenet newsgroup rec.autos.tech, which deals a lot with gasoline and so forth. As with any such post, be sure to tell a little about why you want to know, so they won't think you are trying to take a shortcut on your homework.
Allan Harvey, firstname.lastname@example.org "Don't blame the government for what I say, or vice-versa."
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