Understanding Fuel Consumption Figures and How They're Calculated

January 27, 2012

To make sense of fuel consumption figures, the two most important numbers are the amount of miles traveled and the amount of fuel consumed to get there.

When filling the gas tank, fill until the first click and set the odometer to zero. When arriving at your destination, fill the gas tank until the first click. The odometer reading will show the exact distance covered, and the gas pump will show the exact amount you used to get there. Then divide the distance covered by the amount of fuel consumed, which will show the amount of miles per gallon being traveled.

This gives you an accurate picture of your fuel consumption, but fuel economy includes more than that. Tire inflation affects fuel consumption, and so does how well the transmission is shifting and if the engine is tuned properly. Fuel consumption usually decreases as a vehicle gets older, even if it is well cared for. The weight of the vehicle and a streamlined design both affect fuel consumption, so just driving with the windows closed will improve fuel economy.

Recent cars are all equipped with fuel injection, which metes out the exact amount of fuel more accurately than the old carburetor did, and has helped increase gas mileage on all vehicles. Whenever there has been a fuel crisis that has brought gas prices to new heights, buyers have rushed to buy small economical vehicles. When fuel supplies are plentiful, some buyers will forget any lessons learned and will again purchase larger vehicles with higher fuel consumption.