This one is real simple, but easily goofed up by estimation. What your car's specs are and your actual gas mileage are usually very different. Dirty spark plugs, air filter, fuel injectors, and age of engine, which all reduce your cars miles per gallon, can be causes of this difference. So can the way you drive. A lead footed-hot-rodder who tachs out his gears after every shift will get worse MPG than grandma who never drives over 55 MPH. SO NO CHEATING, or this method of obtaining accurate MPG calculations won't work. Drive as normal. Follow these steps:
- Get paper and pen and put them in the car. You will need to record some specific numbers.
- Wait until your tank is less than a quarter full, then go to your favorite gas station and fill 'er up. NO TOPPING OFF! Lock the gas pump handle while filling and allow it to automatically shut itself off.(Stand back in case it overflows a little. This is rare with newer pumps, but still use caution.)
- After you fill, record on your paper the gas station name and pump number. Service stations have different kinds of pumps, which have different shut off regulators. You MUST return to the SAME gas station and if possible(but not required) the same pump to get an accurate MPG estimate.
- Reset your trip odometer before you leave the gas pump. This is often found in the center of the console gauges, in the center of the speedometer. A stick like button near it should push in and reset the 1000 mile gauge to zero. If you cannot find or don't have a trip odometer, simply get your paper out and record the mileage at the pump, before you leave the gas pump.
- Drive AS NORMAL until you have about a quarter tank left.
- Return to the SAME service station you filled up at, if possible the same pump.
- Fill your car up with gas again, the same way, by locking the gas pump handle while filling and allow it to automatically shut itself off. No topping off.
- On the gas pump, record the number of gallons, including 2 decimals (i.e. 12.05 gallons) used to fill your tank. Don't forget to pay for your gas, because you might be crunching numbers and forget.
- If you set the trip odometer, divide the miles shown on it by the number of gallons of gas it took to fill the tank. For example, if i drove 352 (on the trip odometer) miles and it took 12.06 gallons to refill, 352/12.06=29.19 MPG
- If there is no trip odometer, calculate your miles traveled by subtracting the mileage you recorded at the first fill-up on the odometer from the mileage at the second fill-up. Use this mileage and use the same formula as above.
