* Old oxygen sensors. Oxygen sensors play an important role in regulating the amount of fuel injected into the engine. When they get old or dirty, they can cause the engine to run rich and use more gas than necessary.
* Faulty fuel injectors. Fuel injectors spray fuel into the engine. If they are not functioning properly, they can cause the engine to run rich and use more gas.
* Dirty air filter. A dirty air filter can restrict the amount of air that flows into the engine. This can cause the engine to run rich and use more gas.
* Low tire pressure. Low tire pressure can cause the engine to work harder and use more gas.
* Aggressive driving. Aggressive driving can cause the engine to rev higher and use more gas.
* Idle problems. If your car is idling too high, it can use more gas.
* Faulty thermostat. A faulty thermostat can cause the engine to run cooler than it should. This can cause the engine to use more gas to warm up and stay warm.
* Clogged catalytic converter. A clogged catalytic converter can cause the engine to run less efficiently and use more gas.
* Bad spark plugs or wires. Bad spark plugs or wires can cause the engine to misfire. This can cause the engine to use more gas.
