It's been a couple of months since we bought our car. Since I bought my car, I've been keeping track of our mileage, as well as how often we fill up in gas. The point of this is twofold. First, I am genuinely curious as to what type of gas mileage I am getting out of our vehicle, driving it the way that we drive it. Second, with that information, I want to be able to create a gas mileage budget – an approximation of how much it is going to cost to drive our car each month.

There's two bits of information that you need in order to create this type of budget. The first is the number of kilometres you are driving in between filling up your vehicle. There's two ways to do this. The next time that you fill up your vehicle at the gas station, either write down your odometer reading, or reset the trip odometer. This will give you a base number to start with. Then, just drive normally. Commute, take the kids to school, go to the beach for the weekend. Then, the next time that you fill up, do the same. Write down your car's total kilometres, or write down your car's trip odometer reading (before you reset it). If you are working off your car's total kilometres, then do some quick math and subtract the 1st number from the 2nd. For example, if the 1st reading was 62,345, and the 2nd reading was 62,756, then the number you are looking for is 411. This is the first bit of information that you need.

The second number is a fair bit simpler. It is simply how many litres were consumed in travelling that distance. This number is extremely easy to get, as long as you regularly fill your gas tank up. If you filled up when you took the first odometer reading, and then filled up again at the second, then however many litres of fuel you put into the vehicle at the second fill up is how much fuel was consumed in transit. After you do this a couple of times, you can start creating a chart of your fuel economy. This is what I have so far:

478.9 km 39.739L

432.8 km 33.804L

471.6 km 36.541L

Now, in order to get this into a form that you might recognize and be able to compare to other vehicles, you want to convert this data into the classic Canadian litres per 100km that you will see on new cars for sale. To get this number, simply divide litres by kilometres, and multiply by 100. With that, we get the three numbers 8.28, 7.81 and 7.74. That means that we are consuming, (on average), about 7.94 L for every 100 km that we are driving. That is almost identical to the proposed 7.9L/100km advertised for our vehicle.

For our American friends, to calculate miles per gallon, simply do the same math but replace the kilometres with miles, and the litres with gallons. Also, if you wish to convert your litres per 100km calculation into miles per gallon, you can use this website to do so. With this, I calculated that I am getting just under 30mpg.

What sort of fuel economy are you getting?

Next week: How to take your calculated fuel economy and plan your gas budget around it.

About Alan Schram

Alan Schram writes about personal finance and his encounters with it in his everyday life. Alan is recently married and is looking to save money on expenses and reduce his debts.