For every penny that gas prices go up, Americans spend $1.25 billion more per year at the pump. No one wants to waste that kind of money. So unless you're hauling the whole ball team,  IT'S TIME TO UNLOAD THE OLD SUBURBAN. And you, Honda Element fella, stop smirking: You're getting only 20 mpg—and driving something even less aerodynamic.
If you're driving something that gets reasonable fuel economy, drive it reasonably. When entering a highway,  ACCELERATE TO 60 MPH AT ABOUT DOUBLE YOUR CAR'S TOP 0-TO-60 TIME. As Popular Mechanics proved in a battery of tests, this puts the car in its more efficient top gear quicker than the smug hypermiler crawling up to speed... in the left lane.
 COAST—IN GEAR. The same tests showed that rolling in neutral requires a trickle of gas to keep the engine running but in-gear coasting does not—and that if you anticipate traffic lights and  DON'T COME TO A COMPLETE STOP, you can boost mpg by as much as 50 percent.
A warm engine is more efficient, so string errands together by  DRIVING TO THE FARTHEST DESTINATION FIRST, which will get the block heated up, then work your way home.
When it's warm out, keep cool by opening the windows, enjoying the breeze, and  TURNING OFF THE GAS-DRAINING A/C. At highway speeds, however, our tests showed windows-down driving creates drag. So at 60 mph or faster, roll up the windows and  PUT ON THE A/C.
Notice to hoarders: You don't need to lug around a case of oil, a bag of sand, or that box of antique tools you got at the garage sale, right? So  EMPTY THE TRUNK—less weight, better mileage. Pickup drivers,  REMOVE THE 300-POUND TOOLBOX FROM THE BED and, while you're at it,  CLOSE THE TAILGATE to create a drag-reducing air bubble. MythBusters increased the overall range of a full tank by 30 miles using this technique; the show also proved that  A RIGHT-TURN ONLY ROUTE increases fuel economy by 3 percent, because idling (at stoplights, for instance) wastes fuel. For that same reason,  AVOID TRAFFIC PINCH POINTS. Driving at speed is more fuel efficient than creeping along in low gear. And if you're not regularly carrying a bike or a kayak on that roof rack, reduce drag by  SLIDING OFF THE CROSSBARS or at least  SLIDING THE CROSSBARS ALL THE WAY BACK (making a single wing).
At the pump  AVOID GAS RATED E15; the "E" is for ethanol, which has about 30 percent less energy than gasoline and kills mpg. (Ethanol-free gas is rare today; you'll probably have to settle for E10.) While at the filling station,  INFLATE YOUR TIRES PROPERLY and check them for uneven wear, which works against you. Stickier, wider performance tires also increase road friction and sap mileage. So  STEER CLEAR OF TIRES MEANT FOR RACE CARS, and  SWITCH TO ECO-FOCUSED TIRES, which reduce rolling resistance. Also,  GET A TUNEUP; a smooth-running engine is more efficient.
Finally, don't overlook the obvious: Nothing saves gas like not driving at all.  RIDE YOUR BICYCLE to fetch that quart of milk, especially if the store is just a mile or so away.