If you look at the Environmental Protection Agency’s fuel mileage estimates for the 1994 Honda Civic and the 2014 Civic, you’ll see very little improvement. To make sure we’re comparing apples to apples, let’s look at base-level sedans with a four-speed automatic. You’ll see that when the 1994 was released, it tested at 29 miles per gallon in city driving, 36 mpg in highway driving, and 32 mpg combined. The 2014 tested at 29 mpg city, 38 mpg highway, and 33 mpg combined. With 20 years of technological innovation and rising gas prices, the Civic only gets one more mile per gallon of gas. How can that be?
Certainly the car has gotten heavier over the years, and more technology has been added which can mean more drain on the fuel. But actually, if we dig in a bit deeper, we’ll discover that the Civic has made a bigger improvement than you might think at first. The problem is that in the above comparison, we weren’t really comparing apples to apples, because in 2008, the EPA changed the way fuel mileage is calculated. The Civic has gotten better, but the test has gotten harder.
To understand exactly what the changes in the test are, let’s talk about how the test is done. First of all, the EPA does not perform all the tests itself. Manufacturers test their own cars and report their numbers to the EPA. The EPA tests a number of vehicles independently to, more or less, audit certain claims. The EPA usually checks models that lead in their category, and those that barely escape a gas-guzzler tax – the kind of claims that call for extra scrutiny. Companies who try to game the system can be hit with millions of dollars in fines. With so much at stake, you can usually trust that the reported numbers are generally an honest representation of how the car performed in the test. Ford, Hyundai, and Kia have had recent mileage discrepancies, but the companies took it upon themselves to reimburse their customers.
So, how is the test itself run? The car is hooked up to a dynamometer. A highly trained driver with a sensitive foot has to follow a schedule established by the EPA for each test. The driver is shown a computer display that shows a graph of how fast to drive, and how quickly to accelerate or brake, through each moment of the test. If the driver deviates from the schedule by more than 2 miles per hour at any point, the results are thrown out and the test is run again. Every car is tested with the exact same schedules – as though it were driven in the exact same conditions.
In the old days, there were two test schedules: one with lots of stopping and starting that simulates city driving, and one with higher speeds that simulates highway driving. The top speed in the highway driving test was 60 mph, which, let’s face it, does not represent a top highway speed for many drivers. The city and highway schedules were also run in mild conditions without a lot of other equipment running.
So, in 2008, the EPA introduced new schedules that are supposed to more accurately imitate real driving. There’s a high speed test that reaches 80 mph, a test with the air conditioner running and a 95 degree outside temperature, and a cold condition test. In the cold test, the engine is started cold and the test is performed at 20 degrees. An engine isn’t at its top efficiency until it’s warmed up.
When the new tests came out, Car and Driver noted that it had always had a hard time getting close to the EPA fuel mileage estimates in the magazine’s own tests. With the new test, it was generally able to reach the stated numbers. That tells us that the new numbers more accurately reflect real driving conditions, but it also tells us that the new numbers are lower.
The EPA devised a complicated calculation that could estimate the new mpg measurement from the old one. It allowed manufacturers to run the old test and convert the numbers this way until 2012. This also allows the EPA to estimate the new measurement for older models. You can find these comparisons on the EPA’s website. With the new estimates, the 1994 Civic gets 25 mpg city, 33 mpg highway, and 28 mpg combined.
So when you compare the new measurement for each model – rather than comparing the new test to the old test – the Civic gets about 5 mpg more than it did twenty years ago. A 5 mpg improvement certainly isn’t mind-blowing, but it does look a lot better than if the mileage really had been stagnant over twenty years of development.
Written by Dan Smolinsky.