If you trade-in your vehicle, the dealer will simply roll the old loan into the new loan, increasing your debt load. Plus, when fuel is high, the trade-in value for a gas-guzzler falls. Myth No. 5: Premium-grade gasoline is better than regular gasoline. It depends. Depending upon where you fill-up, premium is 18 cents to 25 cents higher than regular blend. It’s tempting to switch to save a fistful of dollars. But your owner’s manual is your Bible. Follow it to see what blend your car really needs. Back in 1988, 15 percent of passenger cars sold in the US required premium. Today, premium gas accounts for about 9 percent of the gas sold in America today. Here’s the catch. Some vehicles, but not all, operate just fine burning regular-grade gas. There’s a world of difference between “recommended” and “required.” That’s often not the case with many sports and luxury models. The fact is, engines with higher compression ratios need more octane. Ask yourself, is the $4 you save per fill-up worth the engine knocking? Myth No. 6: Set the fuel nozzle on the lowest setting to get more fuel and less air/vapor in your tank True: Station nozzles are designed so that little air/vapor takes the place of the gas you're pumping. If you wish to have a fuller tank, pump more slowly. However, you'll still have to pay for it. Myth No. 7: Hypermiling can improve your gas mileage. False: The goals of hypermiling are positive, such as eliminating aggressive driving and saving energy, notes AAA. Unfortunately, some motorists have taken their desire to improve fuel economy to extremes with techniques that put themselves, as well as their fellow motorists, in danger. Examples of dangerous hypermiling techniques include: * cutting off the vehicle's engine or putting it in neutral to coast on a roadway * tailgating or drafting larger vehicles * rolling through stop signs and driving at erratic and unsafe speeds. These practices, notes AAA, can put motorists in treacherous situations, especially where there’s heavy congestion. You could lose power steering and brakes or be unable to react to quickly changing traffic conditions, putting you into harm's way. Myth No. 8: Over-inflating tires will improve fuel efficiency. False: Over-inflating tires does not improve fuel efficiency, tire makers and highway safety experts, including AAA, say. It merely results in tires wearing more quickly and having less traction on the road. Improve fuel economy by maintaining the recommended pressure. Myth No. 9: A vehicle uses more fuel to shut down/restart than to leave idle. False: When a vehicle is running but not moving, it is achieving negative miles per gallon. In addition, a warm engine uses minimal fuel to shut down and restart. If you're stopping for longer than a minute, it's a good idea to shut down your vehicle. Myth No. 10: Putting the tailgate down on your pickup saves gas. False: You get better mileage with the tailgate up. Counterintuitive but true.