We've all heard it before: have under-inflated tires lowers your gas mileage. I, for one, make an occasional effort to keep my tires properly inflated, and I am always surprised at how much air they lose between checks. Estimates say that the average tires loses 1 psi per month through regular activity. In addition, tire pressure changes with temperature, with an average decrease of 1 psi per every 10 degrees Farenheit.
I became acutely aware of this in the last few weeks. I drive a hybrid, so I get good gas mileage and I also get to fixate on the dashboard display telling me everything I'd ever want to know about my gas mileage. In the last couple of weeks, my gas mileage has dropped over 5 miles per gallon. It was a statistical curiosity until Tuesday night, when my low fuel light started blinking at a very inconvenient location, and about 30 miles before I expected it. Hey, this lower gas mileage is going to have some negative effects on my plans, and also my pocketbook.
I don't drive a lot, only about 300 miles per week. However, if I am getting 45 miles per gallon instead of 50, that means that I need an extra 2/3 of a gallon in a typical week. At $4.00 per gallon, that's an extra couple of bucks per week. Not a lot, but enough to make me take notice.
The only thing I could figure was that perhaps my tire pressure was low. I hadn't checked it in months, and it has gotten awfully cold here. Well, let me tell you. My tires weren't just low, they were really, really low. It only took me about 5 minutes to top up all four drastically under-inflated tires. I figure 5 minutes a week is good for several dollars, right?
Not only does low tire pressure increase your gas mileage, it also increases the wear and tear on your tires. And tires are not inexpensive! Two good reasons to keep an eye on your tire pressure.
When was the last time you checked your tires?
Update, 16 November 2012 - I drove about 100 miles today, and got about 55 miles per gallon instead of 45. Ka-ching!