Fuel savings between 55 mph and 75 mph
07-03-13, 10:21 AM
#1
Fuel savings between 55 mph and 75 mph
The penalty for speeding: A loss in fuel economy
By Consumer Reports News | ConsumerReports.org
Yahoo News Link
By Consumer Reports News | ConsumerReports.org
Yahoo News Link
You know that driving at 75 mph rather than 55 wastes gas, but how much? We did the math, driving a steady 55, 65, and 75 mph in a Honda Accord, a Toyota RAV4, and three versions of a Ford Fusion. The penalty for speeding, even in those relatively fuel efficient cars: a loss of up to 14 mpg.
True, driving 200 miles at 75 instead of 55 shaves an hour off your trip. But in the cars we used, it also wastes 1½ to 2 gallons and costs about $5 to $7. For every thousand miles at 75 mph, you're increasing carbon footprint by 7 to 10 gallons and throwing away about $30.
Need more motivation? High speeds increase the likelihood of a crash and slash the odds of surviving one, says the Insurance Institute for Highway Safety.
Other gas-saving tips. Drive smoothly when possible, avoiding hard acceleration and hard braking. Combine short trips to avoid driving with a cold engine, and keep tires properly inflated. Turn the car off if it will be idling for more than about 30 seconds.
True, driving 200 miles at 75 instead of 55 shaves an hour off your trip. But in the cars we used, it also wastes 1½ to 2 gallons and costs about $5 to $7. For every thousand miles at 75 mph, you're increasing carbon footprint by 7 to 10 gallons and throwing away about $30.
Need more motivation? High speeds increase the likelihood of a crash and slash the odds of surviving one, says the Insurance Institute for Highway Safety.
Other gas-saving tips. Drive smoothly when possible, avoiding hard acceleration and hard braking. Combine short trips to avoid driving with a cold engine, and keep tires properly inflated. Turn the car off if it will be idling for more than about 30 seconds.
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Model 55 mph 65 mph 75 mph mpg% drop between 55-75 Honda Accord LX 4-cyl. 49 mpg 42 mpg 35 mpg 29% Ford Fusion Hybrid 49 41 36 27% Ford Fusion 1.6 4-cyl. 41 36 30 27% Ford Fusion 2.0 4-cyl. 41 34 28 32% Toyota RAV4 37 33 27 27%
07-03-13, 10:34 AM
#2
Lead Lap
No surprises there. These eco-conscious cars are all very speed-sensitive when it comes to hitting their mileage ratings. For me, at this point in life, time is money though and right now it makes sense to continue driving 75mph. 
Provided that it is safe & reasonable to do so.
07-03-13, 12:23 PM
#6
Moderator: LFA, Clubhouse
How about a study from Consumer Reports about how much mpg we lose due to overcrowded highways and traffic during rush hours, as a result of utter government incompetence in allocation of public resources? 
BTW, in the IS F, I only see a 6-10% difference in mpg between 65 and 75 (I've never bothered driving at 55mph). The 8 gears probably helps relative to the case studies here.
Yep. Heck, on the massive interstates, I'd go 100mph if they'd let me.
BTW, in the IS F, I only see a 6-10% difference in mpg between 65 and 75 (I've never bothered driving at 55mph). The 8 gears probably helps relative to the case studies here.
Yep. Heck, on the massive interstates, I'd go 100mph if they'd let me.
Last edited by gengar; 07-03-13 at 12:28 PM.
07-03-13, 12:47 PM
#7
Lexus Champion
This is to be expected with normal automatic or manual transmissions in top gear. The engine will be turning faster at 75mph than 55mph, so it will be using that much more fuel also.
But with a continuously-variable transmission (CVT) (or transmissions with a great number of gear ratios, such as 8- or 9- or 10-speed transmissions) -- assuming it has a great enough gear ratio difference to allow the engine to be turning over at the same RPM at 75mph as at 55mph -- the fuel consumption should theoretically be the same at the two speeds; any differences would be due to increased drag at the higher speed (and I don't know how much effect that will have on fuel consumption).
Does the tested Accord have a CVT? If so, is the gear ratio range great enough to allow for "normal" engine speeds as high as 75mph?
But with a continuously-variable transmission (CVT) (or transmissions with a great number of gear ratios, such as 8- or 9- or 10-speed transmissions) -- assuming it has a great enough gear ratio difference to allow the engine to be turning over at the same RPM at 75mph as at 55mph -- the fuel consumption should theoretically be the same at the two speeds; any differences would be due to increased drag at the higher speed (and I don't know how much effect that will have on fuel consumption).
Does the tested Accord have a CVT? If so, is the gear ratio range great enough to allow for "normal" engine speeds as high as 75mph?
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07-03-13, 01:23 PM
#8
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Aerodynamic drag becomes extremely significant and increases exponentially above 55 mph and especially all the way up to 75 mph. As for the Accord beating out the Fusion Hybrid, remember this is a straight highway driving test and has no city component, so of course the Fusion Hybrid would still clean a non-hybrid's clock there.
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