Jus' curious what is the size of the fuel tank? I have a '74 1.8, I assume they're (stock) all the same. How else does one figure out MPG without this variable.

You don't use the size of the tank. You do something like this: fill up the tank (let the auto shutoff stop the pump). Note the mileage. When you are near empty, fill the tank again (using the same pump would help, but shouldn't be that critical). Note the mileage and subtract the original mileage to get the miles traveled since last fill-up and divide by the gallons needed to fill up. Voila! MPG.

To get the most accuracy, after several fill-ups, add the total mileages and gallons used to average out errors.

Andrew

It's somewhere around 16 gallons. I forget the exact number though.. Doesn't matter to figure mpg. Just fill the tank, drive while keeping track of the miles, then fill again. That many gallons got you that far. Works for any size tank. You might want to use the tire size calculator on this site to find out how far off your odometer is so you can compensate.