How to Calculate Your Gas Mileage

To calculate gas mileage/fuel economy, follow these simple steps:

1. start with a full tank of fuel;
2. note the odometer (odometer #1) reading
3. Drive the vehicle normally and note the use mix (city, highway, or city-highway mixed)
   When the fuel gauge reaches approximately ¼, refill the tank and note the odometer (odometer #2) reading.
4. Subtract odometer #1 from odometer #2; divide the result by the number of gallons purchased.
5. One significant decimal place is sufficient.

Date	Odometer Reading	Miles Driven	Fuel Purchased to Refill (Gal)	Miles Per Gallon (MPG)
5/01/2010	30,455		Fill Tank
5/06/2010	30,723	268	12.7	21.1
5/13/2010	30,983	260	12.4	21.0
5/23/2010	31,302	319	14.8	21.5
6/01/2010	31,597	295	13.4	22.0

Examples: Odometer reads 30,455 when the tank is first filled. The vehicle is driven until the fuel gauge reads ¼ ; the odometer reads 30,723. It took 12.7 gallons to fill the tank again. Subtract the 30,455 from 30,723 and divide the result by the 12.7. [30,723 - 30,455 = 268]

[268 / 12.7 = 21.1 MPG]

You can also try our easy-to-use milage calculator to assist in figuring MPG

The traffic mix — city and highway — affects a vehicle’s MPG. During idle times (times when the engine is running and the vehicle is not moving) the vehicle delivers 0 MPG. Also, each time the vehicle is accelerated, more power (fuel) is required to bring the vehicle to a given speed. The start and stop driving that characterizes in-city driving is, by its very nature, fuel inefficient.

On the highway, speeds are usually steadier resulting in greater fuel economy. The way that the fuel tank is filled can affect fuel economy. Many drivers habitually over fill their tanks, that is they fill them to the very top or “top-it-off”. Vehicles built since 1970 have evaporative emissions control systems. Essentially, these systems eliminate fuel-fume emissions as a result of increased ambient temperatures. The design of this system is to vent excessive tank pressures to an activated charcoal canister and store these fumes instead of venting the excess tank pressure and fumes to the atmosphere. These fumes are eventually burned by the engine thus emissions are reduced and fuel is saved.