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By Robert Rapier on May 1, 2008 with no responses

Inflate Those Tires

Every time I check the pressure in my tires, it is always below the recommended pressure. Every time! And to be honest, it isn’t something I think about on a regular basis. When I had a car, I did get into the habit of keeping a tire gauge in the car. (I presently don’t have a car, as I live within walking distance of my workplace in the Netherlands, but when I return to the U.S. my intention is to get the most fuel efficient car I can find – and to start experimenting with techniques for improving fuel efficiency).

It seems that my experience with tire pressure is certainly not usual. A feature story today at Yahoo Finance has recommendations for improving fuel efficiency:

The 15-Minute Tip: Err on the Side of More Air

The recommendations are to keep your air filter maintained, and echoing the recommendations from my previous essay – overinflate your tires. The story contained this statistic:

The Carnegie Mellon University Sustainable Earth Club studied 81 random vehicles in a parking lot and found that 80 of the 81 had under-inflated tires. The average rate of under-inflation was 20% — soft tires, indeed.

What does that cost?

The EPA estimates that for every 1 psi of under-inflation, fuel economy drops by 0.4%. That’s not much, but if the tires are under-inflated by 8 pounds, that’s a 3.2% drop in fuel economy. About 1.2 billion gallons of fuel are wasted annually due to under-inflated tires, the NHTSA estimated in 2005.

Hundreds of dollars in savings

So, by changing your air filter and pumping up tires that were under-inflated by 8 pounds, you’re likely to get a 13.2% improvement in your fuel mileage.

Take an average U.S. vehicle driven 12,000 miles at 20 miles per gallon. That’s 600 gallons of fuel a year. At $3.60 per gallon, that’s $2,160 a year.

To put that in perspective, that 1.2 billion gallons of wasted fuel is likely greater than what we currently net from ethanol production (net being BTU output of ethanol minus the fossil fuel inputs).

I wish there was an easy way to make sure all tires were properly inflated. Hey, maybe there is a business opportunity there for enterprising young people: After showing them the data on how much it is costing them, make a deal with your neighbors to keep their tires properly inflated.