MPG = (Mileage B - Mileage A)÷Gallons. Subtract Mileage A from Mileage B. This will give you the number of miles you drove since your last fill-up. Divide your answer by the number of gallons (Gallons B) it took to fill up your tank. This will give you your car’s MPG.
Many freeways have “mileage check sections. " They are stretches of road several miles or kilometers long, with mileage markers along the way. If one near you has this feature, use it. Otherwise, look on the map and find a stretch of road or freeway, and mark out an accurate 5 or 10 mile (or kilometer) distance.
At the end of the run, note your trip odometer. An accurate odometer will reflect the distance you traveled. If your odometer is higher than the distance traveled, your fuel efficiency will be better than you had calculated. You actually traveled further than you calculated with just the straight odometer reading. Conversely, if your odometer is lower than the actual distance traveled, your MPG is lower as well.
O=A÷T. For example, if you travel 5 miles, and your odometer says you’ve traveled 4-1/2, your formula would read: O = 5÷4. 5; O=1. 11. To get your actual mileage for your MPG formula, you would subtract Mileage A from Mileage B as normal, then multiply the result by 1. 11 before finishing your MPG calculation. If Mileage B - Mileage A = 100, multiply by O (1. 11). In this example, you actually traveled 111 miles. If your odometer says you traveled 5-1/2 miles, your formula would read: O=5÷5. 5; O=. 91. Again, you would multiply Mileage B - Mileage A by O. If Mileage B - Mileage A = 100, multiply by O (0. 91). In this example, you only traveled 91 miles.
