Every single "Tips for Saving Gas" list tells you to drive 55 mph, but is that really the magic number? By many estimates it's pretty darn close, though each vehicle has its own speed of maximum efficiency dependent on engines, car bodies and driving conditions. Gas mileage decreases rapidly at speeds above 60; boosting your highway speed from 55 to 75 can raise fuel consumption by as much as 20 percent. Driving at steady, reasonable speeds will save both gas and money.

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Excerpted from:

Wake Up and Smell the Planet by Grist.org, edited by Brangien Davis, © 2007 Skipstone.