- I take it your car is carbureted, not fuel injected (MPGuino not an option?)
- Another option which I've seen used: calibrate your fuel gauge with a digital multimeter connected to the sending unit.
- I also assume your car doesn't have the pressurized "return" fuel line, and in-tank fuel pump?
- I've seen a few "Mythbusters" episodes where they use a small removable fuel tank which they weigh between tests to compare consumption.
- And I know of a guy (the guy who built
this streamlined Model T Ford in the 1930's) who put a small graduated fuel container in his car to do the same thing.