With gas prices through the roof, people are paying attention to the mileage that vehicles are likely to get.
Environmental Protection Agency estimates appear in bold print on the stickers in the windows of vehicles in showrooms.
"Can we do better in representing those numbers? Definitely," EPA's Director of Transportation Margo Oge tells Koeppen.
She says the agency is updating its gas mileage test for the first time in 20 years to make it more realistic.
In the meantime, Koeppen says, consumers shouldn't believe its numbers are exact.
The EPA is trying to better simulate real-world driving, things such as driving with your air conditioning on, cold weather, stop-and-go, rapid acceleration, very fast speeds and more.
Current tests are done in a lab.
Until then, the EPA says current figures are good as guides, and for comparison shopping.
David Champion, chief of auto testing for Consumer Reports, showed Koeppen how far off the mark the current numbers can be.
Says Champion, "You really end up with a number, especially the city number, that really is not accurate for today's driving."
That's why Consumer Reports does its own mileage test on every car it reviews.
Champion and Koeppen took a spin in a Honda minivan that the EPA says gets 20 miles per gallon in the city and 28 on the highway. As measured by a device the magazine attaches to engines, it got 28 on the highway, but only 12.3 in city driving conditions.
Champion calls that a "huge" disappointment: "You're gonna be putting almost twice as much gasoline in the car as you thought you would."
He adds that the EPA's city numbers were off in almost every vehicle Consumer Reports tested last year. The EPA rated the Ford Focus sedan at 26; Consumer Reports got 17. The Toyota Camry? EPA got 24. Consumer Reports, 16. The Chevy Trailblazer EXT: 15 as opposed to 9.
But, points out Koeppen, some of the most startling differences were found in hybrids.
For instance, the popular Toyota Prius, which the EPA estimates gets 60 miles per gallon in city driving, only got 35 when the magazine put it to the test.