Q&A for How to Calculate Fuel Consumption

The AC in your car is powered by the alternator in your engine, which uses gasoline to run. So, using your AC uses gas.

Staying in a lower gear actually increases your fuel consumption. So, to save fuel, put your car into a higher gear.

Using an excel spreadsheet or Google sheet, label the top of each column with the information you need to track. For example, your column labels might be "Date," "Odometer Reading," and "Amount of Fuel." When you refuel, simply enter the information under the correct column.

If your car doesn't have a working odometer, download a milage tracking app on your phone like TripLog, MileIQ, or Mileage Expense Log. Or, estimate your distance traveled by plotting out your routes on a GPS or on your phone's map app. Just record the distances you travel for each trip you make until you need to fill up on gas again.

It depends on your car make and model and the engine RPM (revolution speed) and other factors.

The starting mileage is when he last refueled his tank. He had a full tank and drove 389 miles, then refueled with 12.5 gallons. The starting amount is 12,500 because the person did not reset the odometer to 0 before he started. Otherwise, this is the exact same thing in the instructions. He already drove 12,500 miles, and now he drove additional miles; in order to find the distance, you must subtract.

You can only do that if you recorded the mileage on the odometer from the last time you tanked. If not, you will have to record it now as well as the next time you tank. There is no other way if the record was not kept unless you happened to take picture of your dash during your filling.

Keep track of all of the miles you drive on the clock from your starting point all the way to your arrival point. You can do this with the odometer on your car. Find out what your company reimburses per mile and calculate how much you're owed for your reimbursement.