Why Does My Car Have Really Bad Mileage?

There can be many causes for a car giving a bad mileage. First, check the tire pressure of all tires. Is the pressure in all the tires correct?

Check your spark plugs. Are they faulty or worn out?

Check the engine oil. Is the oil level low?

Check the air filters. Are they dirty and clogged?

Check the fuel pump. Is it faulty or creating some noise?

Do you put your car in idle for long periods of time?

Do you frequently drive your car over the speed limit or perform sudden accelerations?

Incorrect tire pressure, be it too low or too high, is a common cause for bad gas mileage and also one of the easiest things to fix. If you have an air compressor at home, you can fix it your self or take it to a technician.

Spark plugs are responsible for creating a combustion in the engine. So, if is faulty or worn out, it can affect your mileage negatively.

A low-level of oil is a possible cause for a bad mileage as it makes a car burn through the fuel faster. So get your oil changed.

A dirty air filter will hamper the combustion process which in turn increases the amount of fuel burned. Change the filter or clean it.

Fuel efficiency also depends on a fuel pump. So if the pump is faulty and not supplying adequate gas to the engine, the efficiency of the car will drop. So better get it checked and fixed.

This could be the cause as even when a car is in idle, the engine is burning fuel. So it is better to turn the car off when not in use.

When a car speeds up suddenly or having a speed of more than 120kmh or 70 to 80 mph, the fuel efficiency decreases by a lot. So keep the acceleration steady and check which speed is optimum to give good mileage for your car.

The problem could be many other things such as a bad oxygen sensor, clogged fuel injectors or a defective mass airflow sensor. So it is better to get your car diagnosed from a technician.