Internal combustion engines depend on gasoline to be able to run. The measurement which manufacturers use to determine how much gas the car will consume over a certain distance is measured in miles per gallon or MPG.
Since engines come in different displacement and configuration, the fuel consumption will vary. With the engine aside, the weight of the car and the transmission will also play a significant role in how much fuel the car will use.
Measuring the MPG of your car is not as simple as checking the number on your dashboard. Even though the numbers are usually not far off, there still might be a few percent discrepancies, so in order to determine, you will need to do the math yourself.
The first thing you should do is to fill up the tank to the top and reset your odometer and start driving your car. Keep note if you are doing city driving or highway and take that into consideration when you do the math. To get the most accurate results, drive your car until it's empty.
Check your car's specs to see how much gallons is your fuel tank and divide the number of miles you drove the car with the number of gallons. Keep in mind that your driving style, weight, and many other factors will have an impact on the MPG result you get.
The rated MPG that the manufacturer provides you is based on a set of tests conducted by the manufacturer itself based on a set of requirements by the EPA.
For the most part, they try to follow the rules and get numbers that are as close to real-world as possible. The problem with that each person has a different driving habit, so you won't always get the same numbers as the ones your car is rated.
It depends on the car. A big V8 will never be as economical as a straight-four. To determine if your gas mileage is bad, you should look at the rated MPG. If you get several MPGs less, then you are good, while if you get half, then that is a bad MPG.
There are many things you can do to save gas. The most common way people save gas is to shift up lower in the rev range. The next thing you should keep an eye out is the tires. Make sure the pressure is as close as possible to what the manufacturer specified. Next up, you should change your driving habits, especially in city driving. Accelerating is what uses the most fuel, so being gentle with the gas pedal can save you some fuel. Follow what is happening in front of you; if you see a red light, don't rush to reach it and then brake. Finally, following the speed limit is another good way to increase your MPGs.