How To Figure Gas Mileage

Hypermiling was the Oxford dictioanry’s word of the year in 2008. This basically means stretching the most mileage out of your car, using any means. Some people would include additives in their fuel, or make modifications on their engines. Some would even use dangerous driving techniques, like coasting (freewheeling) on neutral when going downhill.

Some people save on fuel expenses by driving smart. This will usually include lumping your errands into one trip, carpooling, planning trips, and driving at a moderate pace. Sure, you can replace your car with a hybrid, but that will entail some cost. Driving smart can be just as efficient.

Figuring out your gas mileage is easy enough, with some mathematical knowledge and some knowledge about how your car works. Some cars will have a multi-information display, which automatically gives you the current gas mileage. However, for most cars, you can compute for your mileage by measuring miles travelled per top up.

Mileage defined

Gas mileage is defined as the number of miles (or kilometers) that your car can travel per gallon of gas (or liter). Depending on the standards used in your country, this would either be miles per gallon (MPG) or kilometers per liter (KM/L or KPL).

To compute for gas mileage, you will need to compute how far your car has travelled and divide this figure by the volume of fuel it has consumed.

For example, if your car has travelled 150 miles, and it consumed 5 gallons of fuel through this distance, you have a mileage of 150 divided by 5, or 30 MPG.

How to compute for mileage

Now, the trouble here is that you might not necessarily know how much your car has spent on every trip. Your car manufacturer might give you a rough mileage estimate and rating for your car’s particular make and model. But for all you know, these could just be marketing figures. You want to know how economical your car actually is.

Whether you have a digital or analog fuel gauge, it will not be accurate to the gallon or liter. Here’s a neat trick you can do:

  1. On your next top up, reset your trip meter to zero. This trip meter is usually alongside the car’s odometer. It functions the same way—it will record the distance travelled. The difference is that the odometer cannot be reset, while the trip meter can. This comes in very handy when estimating your travelled distance. Resetting the trip meter will usually involve pushing a button or lever on your instrument panel. On newer cars with digital odometers, you might have to press and hold a button. Refer to your user manual for instructions when in doubt.
  2. Fill ‘er up. Gas up to full tank.
  3. Drive. Drive as you normally would. This can be highway driving, city driving or both. It depends on what type of mileage you want to compute for.
  4. Fill ‘er up when gas gets low. When you pay the bill, keep the receipt, which will usually display how much volume of fuel you got. Or, you can take note of this from the fuel pump display. For best results, use the same refueling station from your prior top-up.
  5. Do some math. Look at the figure you have on your trip meter. Divide this figure by the number of gallons of gas you just filled up with. So, for example, you travelled 80 miles, and you just topped up with 4 gallons of fuel. Your mileage is 80 divided by 4 or 20 MPG.

Your mileage will vary, of course, with the type of vehicle you drive, the engine displacement, and other factors like load, road type, and vehicle modifications. You will usually get the best mileage when your car is regularly serviced, when you have the least load, and when your driving habits are not too aggressive.


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