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Sunday, March 4, 2012

EPA Estimated Fuel Mileage vs. Actual Mileage

EPA Estimated Fuel Mileage vs. Actual Mileage what is the real story or actual numbers that we all should be looking at? For most of us, we tend to think that the large black numbers on a car's window sticker, which list the EPA estimated fuel economy rating, are what they will actually get while driving that car.

But before you believe this, you should in essence, “Read the fine print!” What the fine print really means is that the actual mileage may vary depending on a whole lot of things. And the truth is, that the gas mileage you get could be less, in fact, a lot less.

How do they come up with these gas mileage estimates? Well, the government puts a great deal of time and care into testing for fuel economy. And these estimates provide important information when it comes to comparing two vehicles. What critics say is that, as part of the test program, a number of assumptions were made about driving habits. Those assumptions are now outdated; and that is why we have inconsistencies when comes to EPA estimated fuel mileage vs. actual mileage.

New vehicles are tested by the manufacturer according to guidelines outlined by the EPA. The EPA in turn reviews the results and confirms 10 percent of the test results with additional testing in the National Vehicle and Fuel Emissions Laboratory (NVFEL), in Ann Arbor, Michigan.

The cars are tested by putting the drive wheels on a "dynamometer," a machine that allows it to simulate driving conditions while remaining stationary. The car is tested according to two different "schedules" to produce the city and highway ratings posted on a car's window sticker.

The two schedules are meant to simulate different styles of driving that would be encountered in the two types of driving:

City: The test is started with the car's engine cold. The car then is operated in such a way as to replicate 11 miles of stop-and-go rush-hour traffic. Periods of idling are included in the test; average speed is 20 mph and top speed is 56 mph.

Highway: This test represents 10 miles of a mixture of rural and interstate highway driving. The engine is warmed up before the test begins and the average test speed of about 48 mph is maintained. The top speed reached is 60 mph. No intermediate stops or idling are included in the test.

The EPA fully admits that test results MAY differ from real-world fuel economy ratings. It attributes the difference to the fact that the test cars are in optimal mechanical condition, along with a few other attributes and thus perform better. But by looking at the EPA's testing procedure, it is clear that real world drivers are not duplicated. On most highways, speeds of well over 60 mph are common resulting in much lower fuel economy ratings. Furthermore, although the EPA tried to duplicate city driving by introducing periods of idling, today's congested roads produce far more prolonged stops.

So be sure to read the fine print when it comes EPA Estimated Fuel Mileage vs. Actual Mileage.

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