All you need to know.
W = F X D
Work (energy consumed) = Force (aerodynamic parasite drag) X Distance traveled.
Aerodynamic parasite drag force increases as the Square of the increase in speed.

From 55 mph to 80 mph the speed increase is 1.45. 1.45 squared is 2.11
Over DOUBLE THE ENERGY USED!

Conversely slowing from 80 to 55 (55/80 = .6875   Square this = .473 used)
cuts the energy, fuel burned to less than 1/2.

Jim Messina
Allentown, PA 

Robert L. Christensen*
 
Gasoline prices at this date have crept past $4 per gallon for the cheapest regular. More people are buying fuel efficient and hybrid cars, but for generations Americans have been accustomed to having bigger (and more prestigious) vehicles to haul themselves around. Both domestic and foreign car makers have begun making lighter cars to take advantage of the physical law which says that moving less weight from one spot to another takes less energy. These changes are slowly taking place. More needs to be done now.

I drove 228 highway miles on the Mass pike, NY Thruway at 55-60 MPH and I got over 43 MPG.
Most people are driving just as fast as ever, you can easily save 15% driving slower.

These are my calculations.  The return trip is amazing.  I coasted down a few hills coming out of the Berkshires.
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1.  Hess Station Smithfield, Rt 44, RI  to Hess Station, Oneonta NY
2008/07/12  55-60 MPH
227.8 Miles  5.218 gallons   43.656 MPG
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2.  Hess Station, Oneonta NY  to Hess Station Smithfield Rt 44, RI
2008/07/14  55-60 MPH
227.3 Miles  4.5 gallons  50.511 MPG

Tony Ricci
Rhode Island

Ed note: EPA estimates for Tony's vehicle range from 28 to 33 MPG highway (22-25 city).

As a 72-year-old, I remember WWII, when the speed limit was 45 MPH.  There were signs everywhere which read "Is this Trip Really Necessary?"  We were at war and everyone shared the pain.   If you were caught driving 50 you got a ticket.

In the 70s, there was a common assumption that if you didn't go more than 5 miles over the limit, Smokey would leave you alone.  Since then, no matter if the limit is 55 or 70, drivers think it ok to drive as fast as possible.

We are at war again.  As Pogo said, "We have seen the enemy and it is us."  Lets go Pogo!  And if you don't know Pogo, ask your elders.

Keep up the good work.  I proudly display your bumper sticker.  I'm the white-haired woman in the red Grand Marquis on I-29.

Dolores Palmer