YACT: Do you use 6x the gas if you drive at 6000rpm instead of 1000rpm?

[Don Vito Corleone]

Also, keep in mind that modern cars with electronic fuel injection may not be burning much or any gas at high RPMs, if the car is cruising downhill on its own inertia.

 

[Eli]

No.

The fuel usage curve of an engine looks like a C on its back.

It starts out high at idle, and as you climb into the mid-high idle range, fuel usage actually goes down as the engine's volumetric efficiency increases.

Then once you get passed the mid-high RPM range, it goes sky high.

And then as others have said, if you're talking about the engine and car as one unit, moving.. there are many other factors involved.