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| Re: Acela Speed Question (1037152) | |||
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Re: Acela Speed Question |
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Posted by Teddmann on Tue Feb 15 11:38:35 2011, in response to Re: Acela Speed Question, posted by TransitChuckG on Tue Feb 15 11:17:39 2011. Fuel economy at steady speeds with selected vehicles was studied in 2010. The most recent study indicates greater fuel efficiency at higher speeds than earlier studies; for example, some vehicles achieve better mileage at 65 than at 45 mph (72 rather than 105 km/h), although not their best economy, such as the 1994 Oldsmobile Cutlass, which has its best economy at 55 mph (29.1 mpg), and gets 2 mpg better economy at 65 than at 45 (25 vs 23 mpg). All cars demonstrated decreasing fuel economy beyond 65 mph (105 km/h), with wind resistance the dominant factor, and may save up to 25% by slowing from 70 mph (110 km/h) to 55 mph (89 km/h). However, the proportion of driving on high speed roadways varies from 4% in Ireland to 41% in Netherlands.There were complaints when the U.S. National 55 mph (89 km/h) speed limit was mandated that it could lower, instead of increase fuel economy. The 1997 Toyota Celica got 1 mpg better fuel-efficiency at 65 than it did at 55 (43.5 vs 42.5), although almost 5 mpg better at 60 than at 65 (48.4 vs 43.5), and its best economy (52.6 mpg) at only 25 mph (40 km/h). Other vehicles tested had from 1.4 to 20.2% better fuel-efficiency at 55 mph (89 km/h) vs. 65 mph (105 km/h). Their best economy was reached at speeds of 25 to 55 mph (see graph). 
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