How to Calculate Your Car's Fuel Efficiency (MPG)?

How to Calculate Your Car's Fuel Efficiency (MPG)?

As gas prices rise, fuel efficiency is becoming more and more of a critical factor. Knowing your car's Miles Per Gallon - MPG (that is, how many miles it gets per gallon) can help you determine if it's a gas guzzler that's eating up your cash. Once you figure out the MPG, you can do many useful things, like calculate how much a 10¢ rise in gas prices will affect your budget, how getting a car with better MPG will lower your monthly costs, or if your car is getting fewer MPG than it should, that you need it serviced. We'll show you how to do it.

Calculating Your Own Car's Fuel Efficiency

1. Go to the gas station and fill up the fuel tank. 
This may sting a little, but it is key to getting an accurate reading.

2. Record the mileage. 
Before even pulling away from the pump, write down your current mileage. We will call this Mileage A. 
Let’s assume Mileage A=3117

3. Drive normally. 
To get as accurate a reading as possible, drive until the tank is less than half full. The longer you can go before getting gas, the better.

4. Fill up the tank again. 
Try to use the same station using the same pump as the first fill up, as pumps may be calibrated differently. This time, pay attention to how many gallons it takes to fill up the tank. This is usually shown at the pump. We will call this Gallons. 
Let’s assume Gallons=9.25

5. Record the mileage again. 
This number we will call Mileage B. 
Let’s assume Mileage B=3579

6. Do the math. 
The formula for determining your MPG is this:
  • MPG = (Mileage B - Mileage A)÷Gallons. i.e (3579 – 3117)/9.251=49.94 MPG
  • 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.

*Note: 1 US gal = 3.78541