As the price of gasoline continues to rise the question often arises as to whether it makes financial sense to trade-in a 'gas guzzler' for a more fuel-efficient vehicle. There are many factors that go into that decision, including the cost of the new vehicle, the amount of miles you drive and the cost of fuel. You can calculate your monthly fuel savings based on your current miles per gallon, miles driven per month and cost of fuel and estimate how much you'll save by purchasing a more fuel efficient vehicle and when you'll breakeven on the fuel efficient vehicle purchase.