Outdated Tests Inflate Fuel Efficiency Scores on All Vehicles By PAUL ENG Dec. 10, 2004 - How many miles can your car travel on a single gallon of gas? If you think it's close to the fuel efficiency estimates provided by the Environmental Protection Agency, you'd probably be right. That is, unless you own one of those highly touted hybrid models. The EPA has been reviewing its testing methodology and is asking car makers and other testing organizations to weigh in with their comments and suggestions. Millett says the agency has received a good deal of information and is confident it can propose changes and improvements to its lab procedures by next year. Flawed Fuel Factors But EPA critics, such as the Union of Concerned Scientists in Cambridge, Mass., say the disparities in fuel efficiency numbers for hybrids underscore a much larger problem: That the EPA's fuel efficiency tests are fundamentally flawed for all cars. David Friedman, research director of the group's clean vehicles program, says the basic EPA testing parameters -- designed to capture emissions and pollution data -- are based on driving habits of decades past. "The base test is 30 years old," said Friedman. "I wasn't driving back then, but it was a pretty different world." According to Friedman's group, some of the more glaringly outdated driving assumptions and conditions that are still being used by the EPA in its efficiency tests include: Low highway speeds. The EPA test assumes an average car speed of 48 mph and a maximum of 60 mph. Most state highway speed limits are now set at 65 mph or higher. At those speeds, fuel economy can drop by almost 10 percent to 17 percent, compared to 55 mph. Easy acceleration. The maximum acceleration rate is 3.3 mph per second, or equivalent to taking about 18 seconds to go from 0 to 60 mph. By the EPA's own data, most drivers today accelerate nearly five times harder. The harder the acceleration, the more gas wasted. Overestimated trip lengths. The EPA's "city" tests assume a trip of 7.5 miles. But even recent EPA figures show the average urban drive lasts five miles or even half that, at 2.5 miles. Shorter trips mean car engines do not have the time to warm up and operate efficiently. Exclusion of air conditioning and other accessories. Rare luxury items 30 years ago, air conditioners are practically standard features on nearly every new vehicle in the United States. Heavy use of air conditioning and other accessories mean a severe reduction in fuel efficiency -- especially in stop-and-go traffic conditions. "These testing cycles don't represent how people drive today," said Friedman. "They just aren't realistic." ABC News
It has been pointed out in this group that the Prius tends to get better gas mileage after it is broken in. The first 1000 miles got around 45 mpg. My last 1500 miles got around 50 mpg. However, the comments in the article above seem to be quite true and explain why I will never get 55 mpg for all around driving.
my all around driving will never average 55 mpg either, but this past summer i had no problems averaging that figure once the weather cooled a bit. in the time after heavy air conditioning use (i had mine set at 68 all summer long...wasnt even gonna think about sweat!@!) and before regular use of the heater, i averaged about 55 mpg. most of that driving was done with the windows open because the weather was mild enough to do it. but then throw in the 46 mpg im getting now and i'll be lucky to average 50 mpg for the year. interestingly, i am also tracking mileage in my sisters car and so far im experiencing about a 16% decline from my best tanks of summer and fall. she is only experiencing a 12% drop. but she admits that she uses air conditioning sparingly because her mileage tops out at 22 mpg.
Granted, EPA fuel economy methods are antiquated. However, actual fuel economy reveals much about how a vehicle is operated, not how a vehicle is rated. I just turned 3000 mi on my 2005. The vehicle is averaging 53 mpg (one-half highway at 65-70 mph, one-half surface streets). The other flaw in the method is that it is not just "mpg", but also emissions per mile (kilometer) and operating cost per mile (kilometer). The "substitute oil for knowledge" mentality still permeates our approach to transportation. For long-term sustainability, we need to apply knowledge. EPA is thoroughly confused about its own methods, because EPA still quotes emissions as "grams per mile" (mixing measuring units instead of using one measuring system, SI, the US system of measurement).
I drive a 2002 Prius. I live in Minneapolis, MN, and during the warm months regularly exceed the EPA rating for my model. For the period from April to November of this year I drove about 6600 miles with an average MPG of 51.8. However, I am trying to take maximum advantage of my car, and have modified my driving habits to do so. In addition, I have started to more actively plan trips, so that I minimize the number of short single purpose trips where the engine does not warm up. I personally don't understand the point of articles that criticize the EPA--no single test procedure will meet everyone's needs. As long as the test method is known, individual purchasers can adjust their expectations based on their actual driving habits.
I don't know that I agree that the EPA system is flawed. No test could possibly take into account everyones drivng habits or conditions, and the test results in numbers that I beleive are at least comparable, if not entirely accurate. I have averaged the the EPA highway milage rating on my last 4 cars, which I all drove on the same communte under the same contitions. 2004 Prius, averaging better than highway at 53.5 mpg so far, but haven't done an entire season yet. 2002 VW GTI. I averaged 27 mpg, car was rated 20 City/28 Hghway 1999 Nissan Maxima. I averaged 28 mpg. Car was rated 22/28 1996 Nissan Altima. I averaged 30. Car was rated 24/30. I commute in Denver, mostly on highway, but I usually get stuck in some rush your traffic, so I estimate about 3/4 Highway, 1/4 City driving. So I think I am getting consistently better milage than the EPA test would say I should get. Maybe I'm not a typical drive, but I find the test to be pretty much right on, car after car.
i can plan until 3 days after the fact, but its not going to help me at all. the only way to lengthen my trips would be to crisscross town. sure it will increase my mileage at the expense of driving twice as far??? i dont think so. that line where the EPA has "discovered" that most in town trips are only 2-5 miles in length is the telling statistic. keep in mind, on all trips of less than 1-2 miles i ride my bike if not hauling anything in the summer. but its out of the question in the winter time. (i do not do biking in the rain) well heres my errand list mailbox (3 blocks i always walk or ride even in rain unless its a downpour but this is always combined with another trip in the rain case) gym 1.1 miles grocery stores .4 miles, .8 miles, 1.2 miles or 1.6 miles gas station 1.1 miles movie theater 2 miles mall 1.3 miles hospital .4 mile dentist .9 miles so you see, work being 8.2 miles one way is by far my greatest trip. and i will tell you there is a good 6-8 mpg dropoff for trips under about 4 miles when there is at least a 30-45 minute layover bet stops which unfortunately now consists of more than half my driving.
