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Fuel Economy Ratings vs. Real World Fuel Economy

Fuel gauge

You've just bought a new car with a great fuel economy rating. But after driving it awhile, you do the math and realize you're not getting the fuel economy you saw on the EnerGuide sticker at the dealership.

The car is new, so it doesn't require maintenance - and you're being a very conscientious driver. What gives?

Fortunately, it's not just you! According to Natural Resources Canada, fuel economy ratings are based on a 2-cycle test (a city and a highway test) conducted in controlled conditions that don't really reflect real world driving.

Here, for example, is how the NRC describes the city fuel economy test:

"The highway test simulates a mixture of open highway and rural road driving, with an average speed of 78 km/h and a top speed of 97 km/h. The test runs for approximately 13 minutes and does not include any stops. The test begins from a hot engine start."

I don't know about you - but that doesn't sound much like my last highway trip!

Obviously, the test can't take your personal driving behaviours into account, but it also doesn't compensate for things like:

  • Average seasonal temperatures in your area (particularly the colder months)
  • Running the air conditioner or the heat
  • The weight of your passengers and cargo
  • Rapid acceleration or braking
  • Higher speeds (particularly on the highway test, where most drivers drive closer to 100km/h)

The NRC acknowledges that the 2-cycle test doesn't reflect actual conditions and notes that:

"The fuel consumption values derived from these test cycles are adjusted upwards by 10% (city) and 15% (highway) to more accurately reflect real-world results."

Fuel economy testing is still evolving to become a more accurate and helpful gauge of the real world fuel consumption you can expect from your vehicle. Sometime in the future, NRC will be moving from a 2-cycle test to a 5 cycle-test that will include "cold temperature operation, air conditioner usage, and higher speeds with more rapid acceleration and braking".

In the meantime, fuel economy ratings are still a valuable tool when it comes to selecting your next vehicle! But to make the most of your fuel, it's best to stick to the tried and true methods of improving fuel efficiency. Keep your vehicle in good repair, plan your trips in advance to minimize extra driving and follow the tips in our Ways to Save on Fuel infographic.

Have you purchased a new vehicle recently? Was fuel efficiency a factor? Let us know in the comments.

- Rose R.

Comments

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Laura

Some good tips to improve fuel economy. Mythbusters recently also investigated some tips to save fuel including underinflating tires, smoothly accelerating, turning off your engine when stopped (reduce idle time)as well as reducing highway speeds to about 80 KMH.

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