Fuel consumption rating: what the test really covers

Natural Resources Canada describes the procedure on its page about fuel consumption testing. Five cycles are used: a city cycle, a highway cycle, a cold-temperature operation cycle, a cycle with air conditioning in use and a cycle at higher speed, with faster acceleration and braking.

In other words, cold and air conditioning aren't ignored: they're part of the method. The combined rating you see most often also uses a weighting of 55% city driving and 45% highway driving, as explained on the page Understanding fuel consumption ratings.

This method has evolved: Canada moved from a two-cycle approach to the five-cycle approach, with later adjustments. That's why an older value can't be compared directly with a recent one. Ratings by model and year are listed in the Fuel Consumption Guide and on the Government of Canada's official search tool.

The whole point of a standard is to remove variables so a comparison becomes possible. It therefore can't reflect the real length of a Quebec winter, your terrain, your repeated very short trips, your tires, your load or your driving style. Natural Resources Canada also publishes fuel-efficient driving techniques that show how much driver behaviour matters.

So the difference between rated and actual fuel consumption isn't abnormal in itself. It becomes a question worth asking when it's large and persists under ordinary conditions — see below.

The rating is a standardized comparison tool: two vehicles measured by the same method can be compared on that basis. That's useful when choosing, and that's what it's for.

One precaution, though: vehicles don't all react the same way to cold, speed, terrain or short trips. A ranking based on the ratings won't necessarily carry over identically to your real-world use. Use the ratings to shorten the list, then check the data specific to the models you've shortlisted.

Before buying, start from the official rating for the exact year and configuration. During the test drive, the trip computer gives a clue, not proof: it depends on the period it summarizes. After buying, if you want to measure your actual fuel consumption, compare several fill-ups under similar conditions and note the temperature, city/highway split, tires and load. A one-off gap says almost nothing; a large gap that persists after checking tire pressure and maintenance deserves an inspection.

A vehicle that's several years old can differ from the standardized condition of the vehicle used in official testing. Three things deserve a check: how regularly the vehicle has been serviced, tire condition and pressure, and any modifications — wheels of a different diameter, a permanent roof rack, running boards. Their effect depends on the vehicle and how it's used, and shows up in use rather than being calculable in advance.

Also check the value published for the vehicle's exact year, rather than a neighbouring model year.

A moderate gap is expected. A large, persistent gap, under ordinary conditions and on a well-maintained vehicle, can however point to something else: low tire pressure, a dragging brake, a failing sensor, overdue maintenance. It isn't automatically a mechanical defect, but it isn't automatically normal either.

In that case, have the vehicle checked rather than jumping to conclusions. Our inspection checklist covers the starting points.

The best-documented measures come down to driving and maintenance: keep tires at the recommended pressure, remove accessories that increase aerodynamic drag when they aren't in use, moderate your speed on the highway, and follow the maintenance schedule. Natural Resources Canada details these fuel-efficient driving techniques.

Maintenance itself has a cost: our guide to the annual cost of maintenance puts a number on it. For the most frugal models, see our ranking of used city cars and their fuel consumption.