Factors that go into rating a car’s fuel economy?
When the EPA estimates a car’s fuel economy, how do they drive the car? Do they accelerate slow to get stay in the lower RPMs, and ultimately save more gas, or do they accelerate normally, or even accelerate hard.
When testing highway miles, I’ve heard a cars fuel economy decreases 10% for every 5 miles over 60. Does the EPA test highway MPG at 60mph? 65mph is standard for most states, Michigan, I know, the highway is 70mph. Naturally the mpg is decieving for states where the highway is 70mph, unless the EPA test for the limits of all states?
When on the highway, does the EPA test fuel economy while the car is on cruise control for maxium fuel economy? or do they drive without it?
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Filed under Gas Conservation FAQ by on Mar 10th, 2011. Comment. 
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Comments on Factors that go into rating a car’s fuel economy?
car mfg.. to test their fuel economy drive at the speed of 35
I have read the EPA test is from 55 to 65 use25%more fuel and
65 to 75 uses 25% more fuel but that seems to much more fuel
when testing tire pressure is a factor weight is also, useing
cruse control tuned up engine I believe that 60 miles per hour
would be a good speed for fuel economy
The EPA requires tests cars for mpg on a virtual “course” using dynamometers to add load. During the runs on the pre-programmed course, the car is loaded up with tons of measuring instruments to get data on fuel consumption, emmissions, and tons of other info.
All cars are testing using automated procedures, so things like driver technique, fuel quality, routes, and weather are controlled and eliminated as factors.
The EPA mileage estimates don’t always translate directly to our day-to-day driving, but the are very useful as comparisons between different cars.
In general, cars are made and geared for best efficiency in the 55-65 range. Going too far above 68 or so will usually cut your efficiency.
See here for more information direct from the EPA:
http://www.fueleconomy.gov/feg/how_tested.shtml