I took my Prius in for its 40000 mile service today. As I was signing the paperwork, the service manager asked if there were any issues with my car. I mentioned that ever since I got the new tires last year, my gas mileage was down about 10 percent. Instead of getting 52 – 53 miles per gallon, I was getting 47 to 48.
I know some might think, “You’re complaining about 47 MPG? Are you nuts? I get half that!”
Yes I’m complaining. The Prius only has a 10 gallon tank, and I fill up when I get below 8. That comes to 40 miles or more that I don’t get between fill ups.
When I told the service manager he took on a “you too” expression. Turns out that new California regulations set air pressure standards, and my new tires were set to those standards. Instead of the factory recommended 40 PSI, they were setting the pressure to 33. Some Prius owners were reporting a gas mileage drop of 15 percent.
The purpose of the new regulations was to get tires set to the proper pressure to increase gas mileage and reduce air pollution. Unfortunately for Prius owners the reverse was true. By setting air pressure standards that set the tires outside my car’s design specs and dropping a $75K fine on dealers who ignored the government settings, I got worse mileage and added air pollution.
Fortunately there’s an out. If the owner directs the dealer to set the tire pressure to the factory specs, he can document the instructions, do it, and not pay the fine. I so instructed.
Now I’ll see if my mileage improves.
I agree that it’s dumb to make all cars conform to the same spec, which may be irrelevant for your Prius. But why not get a pump and inflating your tires yourself to the tire pressure indicated in the owner’s manual? Or just inflate the tires at your local gas station?
I would have, had I known that they lowered the pressure. Since I was in for service anyway, I had them do it.