Politicians often seem to think they are so smart. If only they could tell everyone how to live their lives, they could make society so much more efficient. Unfortunately, Barack Obama has this conceit in abundance, and his advice on checking tire pressure is just the latest example.

Like most central planners, Obama feels that he's so much smarter than everyone else.

Obama says that “my Republican opponents — they don’t like to talk about efficiency.” Yet, he is the one who doesn’t really understand efficiency. Looking at only the number of gallons that might be saved, he ignores the other costs that real people have to face everyday.

The news coverage has been all over Obama’s claim. A simple Google News search on noon Wednesday, less than 24 hours after Obama's remarks on Tuesday, found over 300 news stories on Obama’s inflating tires advice to save gas. Headlines have ranged from “Check the Air in Your Tires, Save Money” to “What’s so funny about inflating tires.” Talk radio has talked about little else.

According to fueleconomy.gov, adjusting tire pressures might save “up to 3%” of gas used by cars, not 3 to 4 percent of all the United States' oil consumption as Obama claimed. Americans use about 380 million gallons of gas a day, so up to 11.2 million gallons a day could be saved. Undoubtedly this is an overestimate because just as people have cut back on driving as gas prices have gone up, they have probably already been replacing air filters and checking tire pressures more frequently.

Still at $3.81 a gallon, 11 million gallons seems substantial, potentially a maximum saving of $42 million per day.

But look at some simple numbers. There are about 234 million passenger cars and 4-tire trucks in the United States today. Lets assume that 150 million vehicles would have their tire pressures checked during any given week and that it would take, on average, 5 minutes to check (remove the stem covers, check the pressure, fill up the tires with air when needed, put the covers back, clean your hands). Obviously, it takes more time than that — this is just a conservative estimate.

If 150 million vehicles have this done once a week, it would take 750 million minutes a week, or 12.5 million hours. The average hourly wage in the U.S. is now $18 per hour. Including workers not paid on an hourly rate, the number would be much higher. But at $18 per hour time costs on average, that comes to $225 million.

That amounts to $32.5 million per day. Not much different than the maximum that might be saved in gas costs.

But there is a simpler point. If people aren’t checking their tire pressures constantly, possibly they have a good reason for not doing it. They must believe that their time costs and discomfort from doing this are much greater the savings that they can obtain.

There are also safety issues not quantified here. If all this attention to increasing air pressure in tires causes people to more frequently overinflated their tires, there are also safety problems: you risk blowing out the tires and getting into an accident or at least stranded on the side of the road. Aren’t people’s lives, safety, and time fixing blown tires also worth something?

Of course, there are other factual problems with Obama’s claims. For example, despite his claims to the contrary, the proposed increase in oil production from the Outer Continental Shelf will likely greatly exceed any savings that one can get out of keeping perfectly inflated tires.

Obama is hardly alone in making claims about ”efficiency.” For example, T. Boone Pickens is spending $85 million of his own money advertising for wind power in hope of getting even larger government subsidies. If these alternative energy programs were good investments to reduce use of “foreign oil,” Pickens wouldn’t be trying to get people to sign a petition and the government wouldn't need to subsidize him. Spending money on projects that cost more than the benefits that they produce only make us poorer.

Of course, both Obama and McCain support extensive subsidies for alternative energy. The difference is only a question of the size of the subsidies — with Obama clearly promising much more.

Politicians seem to think that they can micro-manage people’s lives. But people frequently know more about their own lives than central planners do. If Obama ever becomes president, it's a lesson that he and the rest of us will probably have to learn all over again.

Lott is the author of Freedomnomics and a senior research scientist at the University of Maryland. Join the discussion about the piece here.