A few weeks ago, Canadian resident Rachel Perks sent me an email puzzler. Why is it that apparently identical cars—same make, model, engine size, specs, etc. — are advertised with drastically better fuel economy in Canada than in the United States?
To see what I mean, compare the official government fuel ratings in the US versus Canada. Or take my car as an example. It’s a 2003 Honda Civic with a 5-speed manual transmission and a 1.7 litre VTEC engine. The US Environmental Protection Agency says I should expect 27 mpg in the city and 35 mpg on the highway. Natural Resources Canada, however, says 38 mpg city and 48 mpg highway. What’s going on? [Quick technical aside: Canadian car sellers use both litres per kilometre (a vastly superior formulation) and also miles per gallon (the terribly misleading measurement we use in the States).]
As it turns out, the greater part of the explanation is mundane—just a translation error really. Canadians use imperial gallons and Americans use US gallons. An imperial gallon is 20 percent larger than a US gallon, so a Canadian vehicle needs fewer “gallons” to travel the same distance. Problem solved, right?
Actually, no. The volumetric conversion accounts for much of the difference, but not nearly all of it. As it turns out, Canadian fuel efficiency ratings are almost certainly misleading and inflated.
Let’s convert my car’s fuel economy ratings into imperial gallons. (Here’s a handy online converter.) In imperial gallons, I should be getting 34 mpg in the city and 42 mpg on the highway, at least according to the US EPA. Remember, that compares to 38/48 reported by the Canadian authorities. Are cars in Canada really that much more efficient? Almost certainly not.
What seems to be going on is that US fuel economy testing is more rigorous than the testing in Canada. In 2008, the US government introduced more stringent testing procedures that effectively reduced the reported fuel economy of nearly every car on the road. Under the older and less stringent standards that are similar to Canada’s, my car would have rated a 32 mpg city and a 38 mpg highway. (In fact, that’s exactly how it was advertised when I bought it.) Convert that older rating to imperial gallons and I’d be driving a car with an advertised 38/45 fuel economy—pretty close, though still not quite as good, as the 38/48 that Canadian manufacturers advertise.
Most of the basic testing protocols are the same in the two countries (see here and here). Manufacturers use a “dynamometer” to test the vehicles in an indoor laboratory environment. Then they report their findings to the relevant government agencies. The big difference is that the US now requires testing that more closely replicates real-world driving: with faster speeds and acceleration, air-conditioner use, and colder outside temperatures, all of which reduce fuel efficiency.
You could dicker about differences in real-world driving conditions between Canada and the US, but I suspect that the differences are very minor. Even where they are significant, the differences may actually cancel each other out. Speed limits are often a bit higher in the States, but stop-and-go driving may be slightly more common in Canada because there are fewer limited-access highways. Air-conditioning use is probably more common in the US, but cold weather driving is certainly more common in Canada.
Because the Canadian ratings don’t account for real-world driving conditions, car-buyers in Canada are faced with misleading and inflated ratings. In other words, they’re getting sold a bill of goods. Buy a car with the inflated efficiency ratings and you’re likely to consume nearly 15 percent more fuel than you thought you were going to. Over the course of a year, that could that could easily add up to a couple hundred bucks of unexpected expense. (The precise figure depends, of course, on the price of gas, your currency, and your driving habits.)
Needless to say, there’s no reason this disparity should exist. The North American auto market is so tightly linked that manufacturers could very easily report the more stringent US-grade testing results to the Canadian government as well. But until they’re required to by law, car manufacturers have every reason to stick with the inflated numbers in Canada.
A couple hundred bucks a year. Hmm, It’s almost like a carbon tax. Except unlike a carbon tax, the extra expense of inflated fuel efficiency is hidden from view, bad for the environment, and funds oil companies rather than the public. That’s a pretty rotten deal.
Matt the Engineer
Do colder outside temperatures really reduce efficiency? My thermodynamics class taught me otherwise. Colder temperatures result in combustion air taking up a smaller volume before ignition. This allows for more pressure on the piston for the same amount of fuel once that air is heated (by the fuel burning). So does this effect come from oil viscosity at low temperatures? Or from lower tire pressures? I’m honestly curious.(sorry for focusing on a minor point)
Eric de Place
Great question, Matt. The point you make seems sensible. I’ve long heard the cold weather reduces efficiency—though precisely why that is the case is unclear.Here’s what the US EPA says on fueleconomy.gov:”Cold weather and frequent short trips can reduce fuel economy, since your engine doesn’t operate efficiently until it is warmed up. In colder weather, it takes longer for your engine to warm, and on short trips, your vehicle operates a smaller percentage of time at the desired temperature. Note: Letting your car idle to warm-up doesn’t help your fuel economy, it actually uses more fuel and creates more pollution.”Not super helpful. Using my Powers of Google I’ve turned up the following explanations:1. Cold air is denser, so it takes more force to push through it.2. Cold air reduces tire pressure, which creates more drag.3. The engine needs more fuel to stay at its prime operating temperature (though I’m not sure why your thermodynamics point doesn’t negate this one)4. Obviously, if there’s snow or slush on the ground that creates additional drag.5. Cold air increases the viscosity of oil, so it requires more energy to get it to flow. (Many places uses different viscocity oils during the winter.)6. Some places appear to actually sell a slightly different mixture of gasoline during the winter—and this mixture has slightly reduced energy content. 7. There’s more load on the engine from accessories—heater, wipers, defroster, seat warmer, etc.I’m not vouching for these explanations, mind you, just mentioning that they appear often around the Interwebs.
morgan
#5 & #3 are the biggies. It takes far longer (2 or 3x) for the engine oil to reach operating temperature than for the coolant. To maintain desireable levels of performance, the fuel mixture is enrichend during the warm-up phase, which can account for a large portion of driving time. #1 & #7 are barely measurable and less important than, for example, your cruising speed or when you let off the gas before a stop light.#2 doesn’t make any sense, unless one argues that the temp inside the tire is different than outside it.
morgan
I’m a little unclear of what the practical problem would be? If we’re talking about point-of-purchase, aren’t we talking about consumers making choices among products whose efficiency ratings are identically distorted? Does a difference between US and Canadian assessment methods have an effect on consumer choice in, say, Ottawa?
Eric de Place
Hey Morgan,1. Yeah… I’m not vouching for those explanations. So as for #2 I’ll just note that it’s mentioned all over the place. And the air temperature does apparently change inside the tire when it’s driven. (It gets warmer.) 2. I’m not sure how clear I was in the post. The distortion between the US and Canadian ratings doesn’t much matter—that’s not what I was trying to say. I was just using the comparison to show that the rating techniques in Canada are sub-optimal and could easily be improved in stringency, as the US has recently done.The point I wanted to make is that there’s good reason to believe that Canadian consumers are faced with misleading product information. Sure, the fuel-efficiency of vehicles in Canada may be roughly identically distorted, but that distortion really matters. Consumers end up purchasing more harmful and more expensive vehicles than they think they’re getting.
waxner
Needless to say, there’s no reason this disparity should exist. The North American auto market is so tightly linked that manufacturers could very easily report the more stringent U.S.-grade testing results to the Canadian government as well. But until they’re required to by law, car manufacturers have every reason to stick with the inflated numbers in Canada.