B.s.f.c. Bs.....?

I think cruise HP is under 40, for most cars, so that puts mpg at about 20.

One of the best resources for automotive formulas and data is the Bosch automotive handbook. It was a great help in the development of my efi system. Another good book is the Heywood book Internal Combustion Engine Fundamentals. It is old, but done on stationary engines, lots of good data.