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If you notice that there is a sudden drop in the miles per gallon (mpg), it might not be necessary to go straight to a mechanic. Instead, check for some common reasons for sudden mileage decrease that you can be able to fix by yourself without much stress.

Inefficient Driving

Inefficient driving can radically affect your vehicle's gas usage efficiency. Follow the speed limit and try as much as possible to avoid going over 60 miles per hour for long periods of time, as most vehicles tend to get less efficient when they go over that speed, according to the U.S. Department of Energy. If go on a long trip on the interstate highway and you continually drive more than 60 miles per hour, you will notice a drop in the gas mileage you getting from your car.


Before you carry out an oil change, always make sure that you get the correct viscosity for your vehicle. Most vehicle owner's manuals will often state exactly the appropriate type of oil to use for you to get optimum mileage, with names like 5W-30 or 10W-30. If the wrong oil is used, you may notice a reduction in mpg and general poor performance, especially in the cases of extreme heat or cold.

Heavy Loads

If you have been driving with a lot of extra weight in your vehicle, there may likely be a reduction in your gas mileage. According to the Federal Trade Commission, for every 200 pounds of cargo and passengers in that you put in your vehicle, you reduce your mileage by 4 percent. Get rid of excess weight by clearing your trunk, backseats or cargo areas.

Tire Condition

Tires can considerably affect your vehicle's mpg. Carry out regular checks your tires and maintain their pressure at the manufacturer's recommended pressure for optimum gas mileage. This pressure is usually printed right on these tires themselves. Also, note that aging tires which have begun losing tread can result in lower your gas efficiency. If the tires are balding or in a poor condition, have them repaired or replaced.

Thermostat Problems

In the newer model cars, your engine coolant is properly regulated by a computer-run thermostat, but if the thermostat fails or breaks, your vehicle may likely be cooling itself all the time, even when it does need to be doing this. The result is bad performance and poor fuel efficiency. You need to have a mechanic run a diagnostic test on it to figure out the cause of the problem.

Blocked Air Filter

For the older vehicles with carburetors, a filter that is clogged or dirty results in poor air intake. This makes fuel combustion inefficient and consequently the use of more fuel than is necessary. This reduces your mileage and is bad for the engine. If your vehicle does not use a carburetor, a blocked air filter can lead bad acceleration, but will not result in a case of bad mileage.

Efficient Engines