Honda S-Dream Streamliner: 260 mph on ~190 HP

[aerohead]

Originally Posted by Ecky

I wonder what its fuel economy was at that speed.

That's gonna be hard to pin down.The car is continuously under W.O.T. through all the gears over,say,8-miles of acceleration.
The BSFC of the engine will literally all over the 'map.'
The barometric pressure can vary through the day,so air density (drag) will also be varying.
Salt conditions (rolling resistance) can vary all along the course.Racing tire manufacturers do not provide users rolling force coefficients.They'd be meaningless anyway on the salt.
And wind can also vary along the course.
It's one big transient can of worms.
About all we could do is compute an average for the run,based upon the actual consumption.
If you hung out at CRC Racing Fuels you could find out how much they pumped.For record runs,the tanks are sealed by FIA representatives and cannot be touched,except during refueling after impoundment.
You could estimate a 'street' mpg by extrapolating aero and R-R data from this Honda Accord power curve from the mid-1990s
,based upon the Accords highway mpg; using estimated weight,frontal area,and Cd.(this presumes that tires never reach a standing wave).