causes of poor gas mileage

The gas mileage of a vehicle is the amount of miles that vehicle can travel given an amount of fuel. In other words, it is the ratio of the number of miles travelled to the volume of fuel burned in the course of the travel.

There are numerous causes of high/increased fuel consumption. This can make troubleshooting of bad gas mileage difficult for non-experts.

It is important to know the car manufacturer's specified fuel consumption rating so that the thinking that the car consumes fuel will not be as a result of false perception.



1. Worn spark plugs
2. Leaking injector
3. Vacuum leak
4. Binding brakes
5. Poor alignment and wheel balancing
6. Incorrect wheel/tire size
7. Lazy or faulty oxygen/AF sensor
8. Incorrect cooling fan operation (engine overcooling)
9. Aggressive driving habit
10. Stop and go driving
11. Restricted exhaust or exhaust with excessive flow
12. Worn fuel pump
13. Bad fuel pressure regulator
14. Faulty ignition coil
15. Incorrect engine timing
16. Faulty PCV

17. Faulty or dirty MAF/MAP sensor
18. Incorrect engine oil viscosity
19. Extra weight in the car
20. Using lower octane rated fuel in contrast with the recommended octane rating
21. Absence of cooling system thermostat
22. Stiff engine parts like pulleys and belts, air conditioner compressor.
23. Fuel line leakage
24. Incorrect tire pressure
25. Using the wrong gear
26. Faulty engine coolant temperature sensor
27. EGR valve leak
28. Dirty air filter
29. Dirty fuel filter
30. Low engine compression
31. Slipping clutch or transmission
32. Poor aerodynamics
33. Bad fuel
34. Clogged injector
35. Degraded engine oil
36. Fast driving
37. Air conditioner use and air conditioner that is overworked
38. Rolling windows down at top speeds
39. Excessive idling
40. Faulty knock sensor
41. Faulty camshaft sensor
42. Faulty variable timing sensor