We've all heard it ad nauseam - simple ways to boost MPGs without buying a hybrid or ditching your car for the train. Pump more air in the tires, turn off the A/C, change your filter, many 'experts' say, and that dreary gas station will become a less frequent site. But does all this advice really help, or are we fooling ourselves into buying even more petrol?

CNN Money set out to separate fact from fiction by exposing 6 gas-savings myths. The report cautions that some of this so-called expert guidance simply "makes no difference," while some can even "wind up costing you." The article also points out that there are really no substitutes for fuel-efficient vehicles and sound driving habits.

Here's a look at some of the most common gas-saving misconceptions.

#1. Fill your tank in the morning. You may have heard that it's best to fill your gas tank in the early morning while the fuel is cold. The theory goes that fluids are more dense at lower temperatures, so a gallon of cold gas actually has more gas molecules than a gallon of warmer gas. But the temperature of the gasoline as it comes out of the nozzle varies little during the course of the day, according to Consumer Reports, so there's little, if any, benefit, to getting up early to pump gas.

#2. Change your air filter. Maintaining your car is important, but a clean air filter isn't going to save you any gas. Modern engines have computer sensors that automatically adjust the fuel-air mixture as an increasingly clogged air filter chokes off the engine's air supply. While engine power will decrease slightly as the air filter becomes clogged, a lack of performance or an increase in fuel consumption will be negligible, Consumer Reports says.

#3. Use premium fuel. With prices already over $4.00 a gallon, premium gasoline is a hard sell these days. But a lot of drivers think because their owners' manual recommends premium, they'll get better fuel economy with it. Really, they may be paying more money for nothing. Newer cars for which premium is "recommended" - but not "required" - won't suffer with regular fuel. Modern engine technology comes to the rescue again. When sensors detect regular instead of premium fuel, the system automatically adjusts spark plug timing. The result is a slight reduction in peak horsepower - really, you'll never notice - but little or no reduction in fuel economy.

#4. Pump up your tires. Proper tire inflation is important for a number of reasons. Under-inflated tires are bad for handling and can even cause a crash. Improper tire inflation also causes tires to wear out faster and to heat up more, which could trigger a dangerous high-speed blow-out. According to on-the-road driving tests by both Consumer Reports and auto information site Edmunds.com, underinflated tires reduce fuel economy, so proper inflation is key. But you should never over-inflate your tires. They'll get you slightly better fuel economy because there will be less tread touching the road, reducing friction. But that means less grip for braking and turning. The added risk of a crash isn't worth the extra mile a gallon you might gain.

#5. To A/C or not A/C. There's no question air-conditioning makes extra work for the engine, increasing fuel use. But car air conditioners are much more efficient today than they used to be. In around-town driving, using the A/C will drop fuel economy by about a mile a gallon. Meanwhile, driving at higher speeds with the windows down greatly increases aerodynamic drag. As speed increases, drag becomes more of an issue, making A/C use the more efficient choice at high speeds.

#6. Bolt-ons and pour-ins. Before you buy a device that's supposed to make your car more fuel-efficient or pour in an allegedly gas-saving additive, ask yourself this: Don't you think oil and car companies aren't doing everything they can to beat their competitors? If BP (BP) could add something to its gasoline that made cars go farther on a gallon, cars would be lining up at the company's pumps. Sure, people would burn their fuel-saving BP gas more slowly, but then they'd drive right past rivals' gas stations to come back to BP for more. BP stations could even charge more for their gas and still sell tons of the stuff. So if there really was an additive that made gas burn up more slowly, it wouldn't be sold over the Internet one bottle at a time.

To read the entire article, go here.