I was trailing Mike on drag week in a rental car, and I can tell you he's averaged 33mpg twice over different states and this was including his dragstrip passes. His nitrous system was setup for about 200 extra hp, so the Mustang was about 600hp on a street tune with no nitrous. Still faster than any of my piles. Here's a video of him crusin'....I have the rental car floored trying to catch him...LOL
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1982 Chevette diesel
36 hp at the wheels, best 59.6mpg.
1989 Dodge Diesel
972rwhp, 27mpg.
1971 Nova tubbed, solid cam 355 w/nitrous, really bad fuel economy.