In a carburetored engine system, the fuel is mixed with air in the carburetor to create the optimum mix for combustion. If the mix is incorrect, combustion will be inefficient and reduce gas mileage, and the catalytic converter can eventually be damaged. Fuel-injection systems have replaced carburetors in most gasoline automotive engines because of their greater efficiency at creating an accurate fuel-and-air mixture. Vehicles manufactured previous to the 1990s typically have carburetors, however.
Clean the carburetor occasionally with carburetor cleaner, which can be purchased in any auto supply store.
Include a fuel additive such as STP Fuel Injector and Carburetor Treatment about once every 3 months when filling the gas tank.
Replace the air filter as often as the owner's manual specifies, or at least once a year. If you regularly drive on gravel roads or in very dusty areas, check the air filter every few months and replace it if it is starting to look dirty. According to the United States Department of Energy, driving with a dirty air filter can reduce gas mileage by 10 percent.
Clean spark plugs with a wire brush and re-gap them if they have minor to moderate corrosion. Replace the plugs if they have significant corrosion or combustion deposits.
Avoid running out of gas. Any water at the bottom of the tank can get into the carburetor and lower gas mileage.
Use a multigrade oil, identified by a number followed by the letter "W," then another number. An example is 5W-30. This type of oil has a better viscosity index when the temperature changes compared to a single-grade oil. Additionally, use the lightest oil that the owner's manual advises. Cold temperatures in particular call for a lighter oil, because cold air makes oil more viscous.
Allow the vehicle to idle for 30 seconds in cold weather before driving, and then drive slowly until the engine warms up.
Install a block heater to begin warming the engine before you start the car. In cold temperatures, a block heater can improve gas mileage by 10 percent, according to Natural Resources Canada. Cold temperatures disrupt the fuel-to-air ratio in the carburetor.
Use improved-friction oil in the form of synthetic oil, or conventional oil with additives, for the best fuel economy results.
Check your oil when you fill your gas tank, and add oil if necessary. A low oil level can increase engine friction and reduce fuel economy.
Have the oil changed as recommended, usually every 3 months or every 3,000 miles. Dirty oil increases engine friction, and thus reduces gas mileage.
