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Which one is more fuel efficient ??? Driving with a constant speed at 60 mph for an hour OR driving at 65 mph?

www.fueleconomy.gov (http://www.fueleconomy.gov/feg/driveHabits.shtml) shows that fuel efficiency decreases rapidly if driving at higher 60 mph speed limit. But in the other hand, if I drive 65 mph, it will be quicker to get from point A to point B. So if anyone know, please help me to explain. Thanks.

Public Comments

1. it could be affected by rear end ratio or overdrive gearing.its all about the rpm,s higher geared drive trains means less rpm.
2. You are measuring the amount of fuel the car needs to get from point A to B -not the time. The speed you go is relevant to how much resistive forces you create and have to overcome (in this case wind in your face). The faster you go, the more resistance is created and you must overcome it by using more fuel to go the same distance. If you drive at 150 mph you will use the most fuel. If you drive at 50 mph you will use even less fuel. There is a point when you can't get any fuel economy wise as the rolling resistance(semiflat tires, dragging brakes, greased wheel bearings, and other moving parts and pumps require X amount of fuel just to keep them working and you moving. But the wind resistance is out of the picture. Wind resistance is equal to driving up a hill. The faster you want to go and the boxier the car the more wind resistance is created which is like driving up a steeper and steeper hill. You know when riding your bike, the wind blows in your hair, on your clothes, on your body. You have to fight the oncoming wind the faster you go. Soon you cannot go any faster cause the "wind is too strong and is stopping you - too much resistance. You get pooped out by the time you reach your destination "B" - out of gas. Had you pedalled leisurely you could reach destination "B" at a later time, and still have enough energy(or gas) to go on for awhile yet.
3. A lot depends on your particular vehicle. My Honda and Toyota don't change much between 55 & 65 mph. The Honda drops slightly even when I take it up to 90. I drove from Cal to Arizona all night and didn't let it fall much below 90 and I got 32 mpg compared to 33-34 at slower speeds. During the energy crisis of 1974, a national speed limit of 55mph was imposed and it really screwed over the truck drivers because their rigs were geared to run efficiently at 65+, and being that, at the time, trucks consumed over 90% of the diesel made, it didn't make much sense. So, to answer your question, you have to experiment, and figure in the worth of your time.