TodayApril 17, 2022

How the EPA calculates MPG?

gas-guzzling trucks and SUVs

The biggest talk these days is the price of gas and the decline of sales in gas-guzzling trucks and SUVs. Consumers are starting to look at Alternative fuels such as mild hybrids, full-hybrids, gas turbo, diesel, diesel turbo, and hydrogen. Every time I listen to a news story they are telling me how to get better gas mileage out of my car. How about if I just get the gas mileage I thought I paid for when I bought my car?

There is another war brewing and that is the calculation of the Environmental Protection Agency (EPA) figures. A petition was filed by Bluewater Network, an environmental Corporation in California to urge the EPA to start calculating MPG on real-world tests. Russ Long, Director of Bluewater, makes the point “If Corporate America misleads people the government cracks down on them. When the Government misleads the people, no one slaps their hands.”

The discrepancy, Long explains, is in the test itself. “Back in the mid-70s, a test was created, involving a hose connected to the tailpipe, for smog emissions. The EPA uses the same test, but with a different algorithm to create MPG.” Long goes on to say, “Years ago the EPA put in a correction factor of 15 percent because they knew their numbers were overstated.” There are reasons why the numbers have, once again, gone askew. According to Long, they are:

  • Alternative fuels
  • Highway speed limits have increased
  • The algorithm that the EPA uses split’s, giving city driving 55% and 45% to the highway. Suburban sprawl is making city driving greater – to over 60%.
  • City speeds have been decreasing because of congestion.
  • There are more “power drains”, such as air conditioning, radio, and electrical devices that have never been tested.

The cars are not tested with option packages that include a roof rack, tow package and presumably people. Long wants the EPA to do it right this time, “They should design a real-world road track mimicking speed and traffic. That would have a lot more real-world testing with better numbers.” The most notable difference in sticker MPG and the real-world could be hybrids. “Hybrids are not the only culprit, they just brought it to light. I own a 2004 Toyota Prius. I get 36-40mpg in the city and 40-42 on the highway. I bought the car with a sticker that says I’m supposed to get 60 in the city and 51 on the highway.”According to the CAFE website, EPA is responsible for calculating the average fuel economy for each manufacturer. CAFE certification is done either one of two ways: 1) The manufacturer provides it’s own fuel-economy test data, or 2) the EPA will obtain a vehicle and test it in it’s Office of Transportation & Air Quality facility in Ann Arbor, MI. EPA will do actual tests on typically about 30% of the existing vehicle lines, using the same laboratory test that they use to measure exhaust emissions.

The EPAs unadjusted dynamometer values are calculated from the emissions generated during the testing using a carbon balance equation. EPA knows the amount of carbon in the fuel, so by measuring the carbon compounds expelled in the exhaust, they can calculate the fuel economy.

In a paper received by Toyota Motor Corporation, it reads, “Manufacturers are required by law to use the EPA-estimated fuel economy ratings on every Monroney label (window sticker) and must state those ratings in advertising that quotes fuel economy figures.

According to Chris Rundler, Director of EPA and Dan Harrison, Manager of EPA cars, this is not the case. “A Manufacturer can voluntarily use MPG labels of their own if the figures they have are lower.” The operative words, in this case, are “if the figures are lower.”

This is like the IRS telling you that if your W-2 is wrong you can only use the real number if it is larger than reported, thus owing them more money.

Back in 1975, Congress created CAFE. According to the CAFE website, the purpose of CAFE is to reduce energy consumption by increasing the fuel economy of cars and light trucks. Regulating CAFE is the responsibility of two federal agencies: The National Highway Traffic Safety Administration (NHTSA) and the Environmental Protection Agency (EPA). NHTSA sets fuel economy standards for cars and light trucks sold in the U.S.; EPA calculates the average fuel economy for each manufacturer.

CAFE requires each Manufacturer to have an average MPG of all their cars and light trucks. The current passenger car CAFE MPG is 27.5, while light trucks are 20.7 mpg. If the manufacturer doesn’t meet this requirement they are fined. The current fine is $5.50 per a tenth of a mile per gallon for each tenth under the target value times the total volume of those vehicles manufactured for a given model year. Light trucks that exceed 8,500 lbs gross vehicle weight rating (GVWR) do not have to comply with CAFE standards. These vehicles include pickup trucks, sport utility vehicles, and large vans.

Bluewater petitioned the EPA to change it’s calculation methods. Since then the EPA has set up a website to hear from consumers. The EPA is asking for responses from consumers who think their cars are not getting the Miles Per Gallon (MPG) that was on the sticker.

Some of the more poignant responses on the docket have been;

“It is ridiculous that automotive industries can get away with the published standards. Please change them so that I can know what I buy.”

“I am appalled that my tax dollars are being used to fund government operations that have the result of either intentionally lying or, at best, misinforming the public.”

“I recently purchased a 2004 Toyota Prius which I really enjoy driving. Although I have owned the car for only 18 days, I am finding that my MPG is 40 – 45, substantially below the 50 to 60 MPG claimed. I am making every effort to drive the car in a manner that will maximize fuel economy, accelerating slowly and avoiding quick stops. Offering false information based on outdated tests is truly inexcusable. I firmly believe that tests should be revised to reflect expected mileage based upon realistic driving conditions.”

“Fuel economy in the U.S. has decreased over the last 5-10 years, with the popularity of SUVs and other gas guzzlers. At the same time, fuel economy testing has not been revised to take into account recent changes in traffic patterns. True gas mileage rates in the U.S., as experienced in actual driving conditions, are actually much worse than reported on new car labels. If we are to achieve independence from foreign oil, we have to start with knowing how much fuel we are actually using.”

If you would like to participate in this study by voicing your opinion about MPG

Lou Ann Hammond

Lou Ann Hammond is the CEO of Carlist and Driving the Nation. She is the co-host of Real Wheels Washington Post carchat every Friday morning and is the Automotive, energy correspondent for The John Batchelor Show and a Contributor to Automotive Electronics magazine headquartered in Korea. Hammond is a founding member of the Women's World Car of the Year #WWCOTY, and board member of the Women in Automotive.

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