There's a calculator at www.fast-math.org in which you can enter the
estimated mileage (or kilometerage) you drive per year, the mileage
your current car is getting, the mileage a proposed new car will get,
and it will show you how much money you can save. If you already have
a fuel-efficient car, you can have fun running as-ifs and after-the-
fact comparisons.
Take care,
- Jeff -