The Curse of Your Lead Foot

Eco Living
Feb 27th, 2013 | By Aubrey Yee

American drivers have rightfully been pressing for greater fuel economy, and the market is responding. But what most people don’t realize is that the miles per gallon ratings on cars are based on ideal driving conditions, conducted in a laboratory, usually by the car makers themselves. It’s easy to see how these numbers might be idealized. But the Environmental Protection Agency does test the automakers’ stated mpgs and have recently found some significant discrepancies between laboratory and reality.

Last year the EPA made Hyundai and Kia restate their fuel efficiency claims on some 900,000 vehicles in the United States because mileage estimates were found to be overstated by 1 to 6 mpg. The EPA is planning to buy and test a Ford C-Max hybrid based on a Consumer Reports test that showed that its 47-mpg claims were some 8 to 12 mpg off from what a driver would get under ordinary driving conditions.

One of the main reasons for the discrepancy between automakers’ mpg ratings and real-life drivers’ mpg is our desire to drive fast, and faster still. A recent study from the Oak Ridge National Laboratory in Knoxville, Tenn,. has shown that increases in speed of driving decreases the promised fuel economy of your vehicle sometimes significantly.

Brian H. West, a researcher at the lab, explained to, “People really like rules of thumb, and if you’re increasing your speed from 50 to 60 miles an hour, we find for the largest number of vehicles fuel economy will go down about 12 percent.” When you get up to 80 mph you’re looking at a whopping 16% drop in fuel economy.

And perhaps more surprising is the fact that this phenomenon affects both gasoline cars and gas-electric hybrids. West explained that the reduction in fuel economy was consistent across all vehicle classes, with only a 1-2% variation between the most and least gas-efficient vehicles. So a big SUV and a small hybrid will experience the same percentage of loss in fuel economy as driving speed increases.

In the case of hybrids, the gap between ideal and reality is due in part to the fact that hybrids run most efficiently in city driving conditions where the battery can recharge in a stop-and-go environment. On the freeway, they rely more on gasoline for power.

The EPA is trying to revise its testing procedures to close this gap. They now require an 80 mph speed burst during the mpg verification process, but the driving speeds that are used for testing are still lower than what the average American does on a daily basis.

There are some really great eco-driving techniques that you can practice to ensure you’re getting the most fuel economy out of your vehicle. Simple practices likes anticipating traffic, maintaining a steady speed at a low RPM and making sure your tires have the proper pressure can save you tons of money in gas over the long haul. And for those who really want to get the most bang for their buck, there’s hypermiling. People who practice hypermiling make sure that they don’t keep unnecessary heavy objects in their car, they don’t peel out from a cold stop, and they don’t use air conditioning, among other things. So, it’s a matter of how far you want to go, but clearly taming that lead foot will save you money at the pump, guaranteed.

Tagged: sustainable living, hypermiling, what is hypermiling, hybrid vehicles, hybrid electric vehicles, sustainable transportation, fuel economy, gallons per mile, CAFE standards, gas prices, eco driving, Green Living

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