Five car maintenance myths and the money-saving truth

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There is no question that if you want your car to go the distance, you need to take care of it. But even with good intentions, you may be spending extra money on car care that isn't necessary. Here are five maintenance myths and the money-saving truth behind them.  Myth: Change your oil every 3,000 miles.

Reality: Quick-lube shops put those 3,000-mile reminder stickers on the cars after each oil change, but it's usually not necessary. Their profits depend on not low-cost oil changes, but the ability to upsell pricier services. The smart money is on sticking to the service intervals recommended in your car's owner's manual. Under normal driving conditions, most vehicles are designed to go 7,500 miles or more between oil changes. While more frequent oil changing doesn't hurt the engine, it can cost a lot of extra money and consume more petroleum. Learn how to check your engine oil.

Myth: Air conditioning will hurt fuel economy
Reality: There has been much debate about whether to drive with the air conditioner on or keep the windows open in order to save gas. Using the A/C does put more load on the engine, but in our tests, we found just a slight decrease in fuel economy and no measurable difference when opening the windows (open windows do increase aerodynamic drag). However, using the A/C helps keep the driver alert and more comfortable, which is safer for everyone on the road. We say, just use the A/C and don't worry about it.

Myths: You'll get more gas for your money if you fill up in the morning

Reality: A common tip is to buy gasoline in the morning, when the air is cool, rather than in the heat of the day. The theory is that the cooler gasoline will be denser, so you will get more for your money. However, the temperature of the gasoline coming out of the nozzle changes very little, if at all, during any 24-hour period of time since it is stored in underground tanks. So long as the gas station does even a modest business, gas won't heat up much in the pump, and even if so, that is a relatively small amount. For the extra effort to chase cool temperatures, any extra gas you get will be negligible, and making a special trip will certainly burn far more than it would be possible to save. Just buy when it is convenient.

Myth: Inflate tires to the pressure shown on the tire's sidewall.

Reality: The pounds-per-square-inch figure on the side of the tire is the maximum pressure that the tire can safely hold, not the automaker's recommended pressure, which provides the best balance of braking, handling, gas mileage, and ride comfort. That figure is usually found on a doorjamb sticker, in the glove box, or on the fuel-filler door. If the tire pressure is down 10 psi, our testing has shown that it can make a 1 mpg difference in fuel economy. But far more significant is the impact on handling, braking, and wear--all of which can cost you one way or another. Check the tire pressure monthly after the car has been parked for a few hours. (See our Ratings of tire pressure gauges.) 

Myth: Premium gas is better for your car.
Reality: Most vehicles run just fine on regular-grade (87 octane) fuel. Using premium in these cars won't hurt, but it won't improve performance, either. A higher-octane number simply means that the fuel is less prone to pre-ignition problems, so it's often specified for hotter running, high-compression engines. So if your car is designed for 87-octane fuel, don't waste money on premium and if you car recommends (not requires) premium, you can usually get away with using regular. Some cars truly require premium, meaning you're stuck paying extra. Keep this in mind when shopping for your next car.