New to the Forum, and I have an idea

[jdu3]

Yea, I guess from what I've read 55 is not at all common for a crx, maybe 45? The spreadsheet is assuming ideal conditions, which can be varied, like rolling coefficient, etc.

If I increase the rolling coefficients and use diesel efficiency = 0.31 and gas efficiency = 0.26, I get about 45 mpg for a gas crx and 45 mpg for a vw rabbit diesel. Using the aerodynamic and weight properties of the crx and the fuel properties of the diesel yields 61 mpg.

With the current price of fuels you wouldn't be saving much.

3.85/61=6.3 cents a mile vs 3.30/45=7.3 cents a mile.

Unless you used vegetable oil, then you'd be set.