Here's a bunch of busted myths:
Premium gives better gas mileage
Because premium gas has a higher octane rating than midgrade or regular gas, it produces a little more power when burnt.
Designed for performance cars with large, powerful engines, premium also helps minimize the risk of preignition inside highly-stressed, hot engine cylinders.
On a track, the extra boost given by premium can mean a few tenths of a second difference on a lap time.
In the real world, it barely affects performance, or fuel economy.
Consumer Reports advises that premium should only really be used in your car if your owner’s manual mandates it. In our experience, only a handful of everyday cars are tuned to run better on premium.
Open windows kill fuel economy
Windows or Air Conditioning?
It’s a common misconception that winding down windows on your car to provide ventilation creates so much extra drag that your gas mileage falls further than it would if you use the on-board air conditioning.
Not so, says Consumer Reports. Under lab conditions, it tested a honda accord along a test track at 65 mph. Using the air conditioning to keep the car cool impacted gas mileage by a shocking 3mpg.
Keeping the windows open on the other hand, affected gas mileage so little that it was impossible to measure.

Low rolling resistance tires are always best
While tires specially designed to lower rolling resistance can save you a few mpg if properly inflated and maintained, Consumer Reports advises that better tire maintenance and driver habits can easily make up the difference between an energy saving tire and a regular tire.
As it points out, lower rolling resistance tires often perform less well in wet and icy conditions than regular tires, raising your risk of accidents.
The solution, it says, is to look for a good all-round tire that combines good economy, good tire life and good grip.
Warming up the engine before driving is good
If you’re of a certain age, you’ll remember the days when you had to go outside and start your car before driving it to get the engine up to temperature before you asked too much of it.
That was in the days before advanced synthetic oils, fuel injection and electronically-controlled engines, where cold-engine wear was a major issue of premature engine failure.
Nowadays, it isn’t needed, thanks to clever systems designed to get cars up to operating temperature as quickly as possible after you start it, and oils that cling to the cylinder to protect it even when the engine is cold.
Dirty air filters kills gas mileage
Much like warming up your car, dirty air filters did used to impact gas mileage, especially in older, dirtier carbureted engines.
Nowadays however, air flow sensors and computer software carefully manages the air/fuel mix in your car’s engine, ensuring maximum fuel economy is possible regardless of the quality of air.
Where it will make a difference however, is performance. If the air filter is dirty, less air can get into the engine under hard acceleration, meaning your car speeds up more slowly.
Filling up in cold temperatures gets you more gas
The theory here is sound: the colder gasoline is, the denser it is, meaning you should be able to get more gas into your gas tank when the gas and the outside temperature are cold.

Not so, says Consumer Reports. Because gas station tanks are stored underground, the difference you’ll see in the amount of gas you can pump on a hot versus cold day is negligible.
Myths busted, but you’re the number one factor

As Consumer Reports successfully proves, gas mileage isn’t affected that much by many of the tips and tricks you’ll find floating around the Internet today.
Sadly, as with many things, the gas mileage you get out of your car depends on you more than anything else.
Our advice? Try to keep calm when driving, look ahead, and make sure you’re in top form before you step behind the wheel.
A calm, alert driver is always better than a late, agitated one when it comes to gas mileage.