This is a calculator which will help your visitors know the cost of any trip with their cars. The calculator works with international and English units and several currencies. It's appropriate for car related sites.
All the pieces are there; however, this is extension is more for calculating the cost of fuel for a trip. It is a pre-trip calculator.
A fuel mileage calculator uses the distance, fuel consumed and gives the user either MPG and L/100 - post-trip. This extension does something different. If it did in fact calculate fuel mileage, I would have like to use it on my site.