Apply for a credit card which offers gas savings when you use the card for purchases. This works in much the same way that some credit card companies allow you to earn frequent flyer miles when you use their card for purchases.
Join a loyalty club. Some gas stations, department stores and grocery stores offer lower prices when you present their membership card, but keep your eyes open and verify that their prices are really lower than other stations in your neighborhood.
Check the web for deals. Several gasoline price watching websites sites let you find the best deals in your area.
Use the lowest recommended octane for your car. The lower octane gas is cheaper. Most modern cars are engineered to run most efficiently on lower octane fuel, and often recommend not using higher-octane fuel. Check your owner's manual to be sure, as not all car engines should use lowest octane gas.
Mix octanes. In some areas, the lower octane may be too low for your car and the mid-grade or higher octane may be more than what you need. To avoid overpaying and still get the correct octane for your car you can mix the gas. For example, if your car takes 87 octane and the pumps have 85 octane and 89 octane, then when filling your car, fill half the tank with 85 octane and the other half with 89 octane and this will give you an equivalent of 87 octane plus it will save you money because the lower octane gas costs less.
Determine whether gas with ethanol is right for your vehicle
If there is a high proportion of ethanol, the lower energy content of the fuel will almost always lower mileage. However, 10% or less ethanol actually helps gasoline burn more completely, resulting in better economy.
Fuel with ethanol may be more expensive than standard gas, but the minimal price difference is often offset by lower fuel taxes or subsidies.
Ethanol is much better for the environment, however, fuels with ethanol additives can corrode fuel lines in vehicles not designed with ethanol fuels in mind.
Turbocharged cars often get better mileage with ethanol blends. This is because the higher (over 100!) octane of ethanol permits more boost, which means more efficient fuel usage.