To a brighter future

To a brighter future

Tuesday, March 13, 2012

How to measure your vehicle's fuel consumption. (updated for 2017)

To use less fuel you should know
how much you use now.

Fuel consumption numbers for your vehicle are something you could look up on a site like Natural Resources Canada or Those are the official Canadian and U.S. government sites for fuel efficiency ratings. But why use the government's numbers when it's much more satisfying -- and accurate -- to measure this yourself?

Earlier I suggested that when you drive, you should record your mileage and fuel purchases: this helps you to plan more and drive less. Today we refine your record-keeping and add to it.

Fuel consumption & fuel economy: cousins, not twins.

Now before we get all calculating, I'll be clear. We're looking at  fuel consumption, how much fuel you use to get around. That's related to fuel economy or fuel efficiency (they're, ahem, ... "reciprocal quantities") but not the same thing: look here >>>

Why do you want to know how much fuel you use?

Once you know your vehicle's fuel consumption, you can really commit to lowering it. The numbers make it real: measuring, recording and crunching the numbers makes them yours, so it's personal! Also, once you know fuel consumption you can convert it into fuel economy measures like mpg (miles per gallon) and mpg-imp (miles per imperial gallon). That helps you compare your vehicle to others in cases where they don't use L/100 km.  Plus it gives you another way of looking at how you use fuel. It puts your fuel use down on paper and motivates you to cut it back.

How do you do it?

First of all, keep recording your daily mileage and fuel purchases with that pen and paper (or booklet) you keep in the glove compartment. It's an on-going record of fuel use that lets you figure out your long-term average fuel use (such as a full year), zoom in on a specific time frame (like your summer vacation) or serve as data back-up if you mess up the cool technique I'm about to describe. The cool technique takes discipline and tight control over your vehicle's instrument cluster. And you have to keep your receipts. Are you ready for that?

I hear yes.

Cool Technique for Measuring Fuel Consumption

Start here.
Next time you buy fuel, fill 'er up. Do this every time you buy you buy fuel, forever.

Fill 'er up. Every time.

Now do this...
On the back of the receipt write down how many litres of fuel you bought and your total mileage. In this example total mileage is 141 577 km. Now look at the other number, 415.0 km. That's trip mileage, and the first time you do this it's meaningless: you can't use it. But you'll need it every time after this, so starting next time write it down too.

Total mileage is 141 577 km. Trip mileage is 415.0 km.

 then do this ...

 We need to reset the trip counter to 0 so it can start measuring how far you drive. This usually means holding in the long button next to the display until the number goes to 0.

Reset the trip counter to 0 by holding this button in.

... and you're ready!

From here onward, every time you buy fuel remember these points, in this order:
  1. Always fill the tank.
  2. Record how many litres you bought, total mileage and trip mileage. Either on the receipt or in the booklet.
  3. Reset the trip counter after you get the mileages, and before you leave the gas station. Every time.

So that's the cool approach to measuring fuel consumption, and we're done for now. Next blog I'll explain how to use the numbers you wrote down. You'll be a fuel consumption Jedi!

Dave K

Btw, there's still time to join us for Getting There Green Day 2017.
It's free, it's fun and it's for a great cause!