Now, who would have ever thought it... tsk, tsk, tsk. Pain At The Pump: Government Gas Secrets Government Gas Secrets Mon May 8, 1:42 PM ET The government has been keeping a secret about automobiles under wraps for the past 30 years. Reporter Michelle Meredith teamed up with Consumer Reports to explain why your car probably does not get the mileage advertised. The Consumer Reports' auto test track in Connecticut looks like it could be a new theme park in Orlando. And when it comes to testing cars, Consumer Reports leaves no stone unturned, no lug nut loose. And here's the question Consumer Reports set out to answer -- does your car get the gas mileage promised on the showroom sticker. It's the mileage you probably used to decide if the car fit your monthly budget. First, Meredith took a look at how carmakers come up with these numbers because you could be in for a big surprise. The guidelines for the tests were set by the federal government decades ago, in the late 1970s. Gerald Ford was president and disco was king. And under these guidelines by the Environmental Protection Agency, carmakers are allowed to test miles per gallon by running the vehicle not on the road, but on what's essentially a treadmill for cars. During an EPA spot check, the car ran with no air conditioning, no inclines or hills, no wind resistance and at speeds no greater than 60 mph. There's hardly anything real world about it, but it gives carmakers what they want -- the highest possible miles per gallon to put on that sticker. "People are going into showrooms, they're looking at that sticker that says miles per gallon and they're saying, 'Oh it get goods miles per gallon,'" said Consumer Reports' David Champion. "In reality, they're being cheated." Consumer Reports conducts their test on a track and in the real world. First, they put them through a simulated city course. Next the highway -- a real highway. For the third test, they take the car out on a 150-mile day trip throughout Connecticut. All the while, a special miles per gallon meter is ticking away. Their results? Many numbers you see on those stickers are off way off -- one as much as 50 percent. For example, Chrysler says the four-wheel drive diesel version of the Jeep Liberty gets 22 mpg in the city. Consumer Reports tested it and found it got more like 11 mpg. Honda claims its hybrid Civic sedan gets 48 mpg in the city. Consumer Reports found it only gets 26 mpg -- a 46 percent difference. Chevy's Trailblazer EXT four-wheel drive is supposed to get 15 mpg in the city. For Consumer Reports, it was 9 mpg. "It's an unrealistic sales and marketing tool that they are actually using. They are saying you're going to get 35 mpg, and you're really only going to get 21," Champion said. Why is this allowed? Meredith asked the EPA's director of transportation. "We cannot have a perfect test," said Margo Oge. Oge said for so long, nobody really complained. Meanwhile, everything has changed. "All the cars today have air conditioning, which was not the case in the mid-80s, and we drive at higher speeds because we are allowed to drive a higher speeds. And technology has changed," Oge said. Carmakers know their number is up. Several have been to Consumer Reports' test track to see how they test real world conditions. "I think it's desperately time for a change," Champion said. The EPA has said a change is coming in time for the 2008 models, but is that soon enough? Consumers need real world tests with real world numbers now because with the price of gas constantly climbing, the real world has become a very ugly place. The EPA said even though the new test will reflect more real-world conditions, there is no perfect test. For more information and for a list of the most fuel efficient cars and SUVs, check out Consumer Reports' special report A Guide To Stretching Your Fuel Dollars.