Does driving at 55 mph really saves more gas than driving at 65 mph?

Question

I keep hearing in the news everyone should drive slower to improve fuel millage. Is this really true? How do they base such claim? I can see that if you drive for an hour at a speed of 55 mph you are going to save gas compare to 65 mph. But if you are going from point A to point B that does not make sense. Think about it. If the distance from point A to point B is 65 miles, driving at 65 mph will take an hour to get to point B. If you drive at 55 mph, after an hour you save gas compare to the person going 65, but you still have travel another 10 miles. What do you think? Does this makes sense?

Answer 1

Just do the math.If your car gets 20 mpg at 65mph it will take 3.25 gallons to go 65 miles.Now say at 55mph your car will get 25 mpg.That 65 miles will only use 2.6 gallons.Plus your only talking a few minutes difference in driving time.Sounds like a good deal to me to save a few dollars in gas.

Answer 2

The savings and improved efficiency comes about due to the reduction in wind resistance experienced by the car going 55 verses 65.  It really does make that much difference.

Answer 3

There is a certain point at which a car's engine reaches an optimal point of speed versus efficiency. This may be graphed (as a "College Guy", you shouldn't be too surprised to find that it resembles a "bell curve"), where you would fine that efficiency is very low at the beginning of the car's acceleration, because the engine has to work hard to get the initial momentum, then reaches a peak where the engine has gained its optimal efficiency at a certain speed (55 for most vehicles), then the efficiency falls because energy is being wasted trying to keep the vehicle at higher (i.e., unnecessary) velocities.

In other words, you can only go so fast,

before it becomes inefficient to go any faster.

BTW, other factors also apply.  For example, given the same weight, a 4-cylinder engine would have to work much harder than an 8-cyl to achieve initial momentum and maintain it over longer periods of time. Thus, eventually, the 4-cyl engine would also wear out sooner than the 8-cyl engine (assuming, of course, that regular maintenance is applied to both engines).

The common misconception is that if you are driving fast, you will get to your destination sooner, therefore, it must be more "efficient".  In this instance, the time an individual saves has nothing to do with an engine's capability to perform work (ever hear of a little thing called "E=mc hammer" . . . I mean: "squared"? <g>). The only "efficiency" is the travel time saved, which, of course, could easily be lengthened by a breakdown (due to driving too fast and overworking the engine), an accident (due to driving too fast and losing control or not being able to brake in time), or being pulled over for speeding!

And, if you're wondering why the gov't allows folks to go faster than 55 on some highways, that has nothing to do with a vehicle's engine efficiency, either! (if the gov't gave a darn about fuel efficiency, we would have had a sensible looking, 50 mpg, passenger vehicle, long ago!) It is solely because on less-traveled highways, it is silly to drive slower, simply because there is not as much traffic around. Really!

Check out the following links,

some of which definitely requires a college education!

Answer 4

Yes, on a gallons used per mile traveled basis, regardless of time, driving slower generally uses less fuel.

Answer 5

The amount of gas you pump into the engine is directly related to how hard you push the gas pedal. Learn more at http://issuesof08.blogspot.com/2008/06/g... Be sure to vote in their poll about gas prices, too!

Answer 6

Definitely! See more money saving tips on how to make your vehicle more fuel efficient. http://www.ehow.com/how_2362636_save-mon...

Answer 7

try it yourself, it's not rocket science, and no your theory doesnt make sense, you measure mileage by miles per gallon of fuel used, NOT by time traveled.

usually about 15% savings, and that is proven

Answer 8

no.  that makes no sense. it is TRUE that driving 55 WILL save you gas. It's not based on distance. Of course, in your example the guy going 55 will still have to travel an extra 10 miles. However, the engine has to work about 3 times as hard to stay up at 65 then it would to stay at 55. This has to do with a direct correlation between speed and tourqe. However, you are not smart enough to understand that, so let's just say YES, it will really save you a lot.

Answer 9

Lower RPMs means money in your pocket.