- Spark Plugs
- Spark Plug Wires
Faulty plugs and wires can affect your MPG by 10%
- Air Filter
A dirty air filter can affect your MPG by about 5%. They are usually less then $10, so just replace it with a new one. A dirty one basically "chokes" your engine.
- Fuel Filter
Same deal as the air filter, but a little more expensive....usually around $20
- Upstream O2 Sensor (before cat converter)
The only O2 sensor that affects your MPG is the upstream sensor before the converter (closest one to the engine). With age and use, they tend to wear out and not function as good as a new one. Replacing an old O2 sensor can sometimes help out your MPG. DO NOT use a "universal" one.
- Engine Oil
For fuel economy, its best to run lower viscosity oils. I personally run Mobile 1 Synthetic 5w30. Heavier oils put more resistance inside the engine, directly affecting fuel economy.
- Transmission Filter / Fluid
For automatic transmissions, dirty fluid or worn out fluid can cause the transmission to work harder.
- Rear Diff Fluid
Clean GL5 has less resistance, and allows the gears to spin more freely.
Replacing your stock crank pulley with a lighweight (not undersize) pulley will help you out a bit.
For 5 speed cars, installing a lightweight flywheel will help out. It reduces rotating mass on the engine. Basically does the same thing as a lightweight crank pulley, but on a much bigger scale.
Replacing your stock ignition with MSD will burn your fuel better, resulting in better MPG
If your car is out of alignment, there is more rolling resistance on the tires, causing the engine to work harder to move the car. If your alignment is out in the rear, its almost like your back tires are pulled, instead of rolling straight.
- Tire Pressure
Higher tire pressures have less rolling resistance. I wouldn't go above 35PSI though.
- Wheel Bearings
A bad wheel bearing will cause the same kind of problems as low tire pressure.
Brakes that "stick" and don't release like they should cause the engine to work harder to start rolling the tires.
- Cruise Control
Use your cruise control. When you drive at a steady speed, you use less gas.
- Lead Foot
Its been said that your fuel economy drastically drops after 55MPH. Don't drive like a bat out of hell.
- Route Selection
What roads you travel on have a big impact on your gas mileage. Try choosing straight, flat roads instead of hills and curves. As well, the more "stop and go" traffic you're in, the more gas you will use.
- Check Engine Light
Is your check engine light on? If so, its going to directly have an impact on your fuel economy. Get whatever is wrong fixed, and you will see an increase in fuel economy.