When new vehicles are in dealerships, city and highway fuel economy is boldly displayed to entice buyers. Unfortunately, as the vehicle ages, the number of miles obtained per gallon of gas may decrease. A sudden decrease in gas mileage is a good indication of a mechanical problem. While an actual leak in a fuel line could occur, several areas can be checked to improve fuel economy and keep a vehicle running at its peak performance.
Tune up
Consider when the last tune-up was performed on the vehicle. Newer cars do not require the same tune-up steps that vehicles did 30 years ago. This can sometimes result in maintenance being overlooked. New spark plugs and a clean fuel system can make an enormous difference in fuel economy. Simply replacing four plugs in a Plymouth Breeze and running one container of fuel cleaner through the tank increased my gas mileage by five miles per gallon at a cost of less than $15. Timing issues and a dirty air filter can also present fuel economy problems. However, an air filter does not affect a fuel-injected engine to the same extent it will a carbureted engine.
Oxygen sensors can have an extreme affect on a vehicle’s fuel economy. The miles per gallon of efficiency may decrease up to 40% if the sensors are not working correctly. Before replacing what can be expensive parts, take the vehicle in for a diagnostic test. Many auto parts stores will run this quick test at no charge. The test equipment plugs into a connector under the car’s dashboard. Newer vehicles may have one, two or more sensors, so replacing them when they are not defective is not only expensive but it will not improve fuel economy.
One very easy way to ensure the best fuel economy is by keeping the vehicle’s tires inflated to the recommended pressure. Check the pressure approximately once a month when the tires are in a cold state. This does not mean the outside temperature but the actual temperature of the tires. Driving the vehicle for even one mile can warm the air in the tires. If the tires are under inflated by only one pound, mileage can be reduced by 0.3%. Proper inflation can result in up to a 3% increase in economy.
Fuel caps
Finally, the fuel cap for the vehicle is designed to keep gasoline vapors inside the tank. While used as part of the emission control system, gasoline evaporation could be the reason for a sudden decrease in the number of miles per gallon. Some parts stores or local emission control stations have equipment to test fuel caps. At the same time, a new fuel cap is not normally expensive. If in doubt of the cap’s condition, replacement might be the best choice.
Resource:
Effect of Intake Air Filter Condition on Vehicle Fuel Economy by the Energy and Transportation Science Division.
