From Power Line:

Barack Obama is a lot like Sean Penn or George Clooney. If you give him a script, he can deliver it pretty well. But if he tries to talk without a script that has been written for him by others, he quickly reveals that he is poorly-informed if not downright ignorant. Today he delivered another classic, by claiming that if only we would all properly inflate our tires, we could save as much gasoline as "all the oil that they’re talking about getting off drilling.

Just for fun, I did the math. Properly inflating your tires can improve gas mileage by 3%. Of course, many people already keep their tires properly inflated, and many more are at least close to being properly inflated. Let’s be generous and assume that one-half of the total possible savings would be realized if we all inflated our tires properly; that’s a net gain of 1.5% fuel efficiency.

Americans drive approximately 2,880 billion miles per year. If we average 24 mpg, we use around 120 billion gallons of gasoline in our vehicles. If, through perfect tire inflation, we improved our collective fuel efficiency by 1.5%, that would be 1.8 billion gallons. A barrel of oil produces around 20 gallons of gasoline, so the total savings available through tire inflation is approximately 90,000,000 barrels of oil annually.

How does this stack up against "all the oil that they’re talking about getting off drilling?"

ANWR: 10 billion barrels
Outer Continental Shelf: 18 billion barrels (estimated; the actual total is undoubtedly much higher, since exploration has been banned)
Oil shale: 1 trillion barrels

So, on the above assumptions, it would take only 11,308 years of proper tire inflation to equal "all the oil that they’re talking about getting off drilling."

Obama is a curious case. He gives the impression of being an intelligent guy, but through his unscripted comments we have learned that he knows little about history, science or mathematics. He also seems rather shockingly short on common sense, as this most recent gaffe illustrates.