How to Really Find Cheap Gas

With gas prices rising, cheap fuel is all the more important. To find it, start with the price per gallon. There are plenty of websites that offer this information, but simply keeping your eyes peeled can work well--a lot of websites rely on user input to get their prices and they aren't always complete or up to date. You may find lower prices by being observant.

Having the price per gallon leaves open the question how large a gallon you're getting. Officially, a gallon is 231 cubic inches. But it would seem that not all gas stations calibrate their pumps to deliver the same size "gallon." If you watch your mileage closely and buy gas at several stations posting cheap prices, you may learn that some stations routinely pump more "gallons" into your tank than others. This means they are selling a smaller "gallon." Obviously, you want to buy the largest "gallon" you can.

To figure out which stations sell smaller gallons and which sell larger ones, keep track of your mileage between fill-ups. Using the trip odometer on your car may be the easiest way of doing this. Keep track of how many gallons go into your tank with each fill-up and calculate the mileage. Ideally, for the sake of consistency, you should use the same pump at each station you buy from and never overfill the tank. Buy at several cheap stations and then compare your mileage calculations. If one station stands out as giving you lower mileage (by selling you more gallons per fill-up), it may use a small "gallon." Conversely, if a particular station stands out in giving you good mileage (by selling fewer gallons per fill-up), it may use a larger "gallon."

I've noticed that there can be apparent differences of perhaps as much as 10% or more in the size of the "gallons" sold by different stations. With gas prices levitating above $3 per gallon, a "gallon" that's 10% smaller than a true gallon is actually more expensive if its posted price is as much as $0.30 lower than a station selling a true gallon. Since a price break of 30 cents per gallon will capture the attention of almost any reasonably sentient driver, the size of the gallon at a particular station really does matter.

If you have the same experience (i.e., either large or small gallons) several times at a particular station, you will have probably discovered a chiseler, or, alternatively, an honest station operator. Then, you'll know where to buy gas, and where not to.