Over the years I've heard several different versions of this conversation:
It seems like I'm buying gas more and more often these days. I'm assuming my gas mileage is declining, but I don't know why.
Have you checked your tire pressure recently?
Tire pressure? They look fine, why would I need to check their pressure? Why would it change?
Unfortunately far too many of us drive every day with the assumption that our tires are properly inflated. Thirty percent of us, according to the National Highway Traffic Safety Administration, have at least one tire that's low by 8 psi or more. This is bad news for fuel economy and our consumption of oil — we annually waste 1.2 billion gallons of gas according to the U.S. Department of Energy. Bad tire pressure also increases the odds of blowouts and other types of tire failure that can be a real pain, if not a serious risk to safety.
So, when was the last time you checked your tire pressure? Two months ago? Six months ago? Ever?
Here's the good news: checking your tire pressure is easy as checking your oil or filling your gas tank. Here's the better news: keeping it right can have a significant impact on your vehicle's fuel economy, a kick of up to 3. Keep it right and you'll have to buy less gas, and the savings will ultimately amount to paying about 10 cents less per gallon. So, for safety, savings and fuel economy, checking your tire pressure ought to be a fundamental strategy in the game that is getting better mpg.
For numerous reasons, our tires generally lose about 1 to 2 psi every month. Lose 1 psi in all four tires, and your fuel economy will fall by 0.4 percent. So get a digital tire pressure gauge and use it every month.
It's important to check the pressure when your tires are cold, which doesn't mean when it's cold outside but rather a few hours since they last pounded the pavement. If you live near a gas station with an air pump, the simplest thing is to check your pressure before you go, then get air there if need be. If you have to drive several miles to get to an air pump, check your pressure again when the tires are warm to give you a relative change form the cold reading that will tell you how much more or less you need to put in.
Why a digital gauge? As cool as I thought the pencil-style sliding stick gauges were when I got my first as a kid, I quickly realized they'll give you different readings just about every time. Digital gauges are far more accurate and easier to use. Click here to read more about them.
How do you know the right pressure? Look for a small sticker near or on the driver's door or in the glovebox. It will tell you the idea cold pressure for your vehicle. Sometimes there will be one number for the front tires and another for the back. Either way, that's the number you want; don't be tempted by the number actually stamped on your tires. It's the maximum pressure those tires can handle.
John Rockhold is a green car enthusiast and Contributing Editor for MOTHER EARTH NEWS. Find him on Google+.