In article .com>,
javawizard > wrote:

> 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 -

It's actually a very simple calculation by just applying the mileage
ratio to your current gas costs. I've done it in Canadian units, but the
same idea could easily be modified for the imperial gallon or the tiny
USA gallon.

For example I now spend $1,200 per year on gas, driving 1,000 kms per
month.
My car is 8L/100 highway and 12.5L/100 city.
I drive 80% city, so my effective consumption is 11.6.
If a new smaller more efficient car is 7/10.5L/100 it's effective
consumption for me is 9.8L/100.
Therefore my gas cost with the new car is 1,200*9.6/11.6=$993
for a saving of $207 per year. A 17% saving, not a big deal for my low
mileage.
Tuning this figure up you could increase the saving to reflect the
expected increase in gas cost.