Politics

Good Question: Can Tire Pressure Solve Oil Crisis?

(WCCO) Do we need more air in our tires or less hot air from politicians? The debate over tire gauges and fuel economy made us wonder, how important is tire pressure?

"We could save all the oil that they're talking about getting off drilling, if everybody was just inflating their tires," said Sen. Barack Obama, democratic candidate for president.

Republican Sen. John McCain countered, "We're not going to achieve energy independence by inflating our tires."

According to the United States Department of Energy, "You can improve your gas mileage by around 3.3 percent by keeping your tires inflated to the proper pressure."

They claim that under-inflated tires can lower gas mileage by 0.4 percent for every 1 psi drop in pressure in all four tires.

Energy and Environmental Analysis, Inc. performed the analysis for the Department of Energy. A spokesperson said she was unable to provide an expert to WCCO to explain how the company came up with that data.

"It'll have some effect," said Dr. Craig Shankwitz, mechanical engineer with the Center for Transportation Studies at the University of Minnesota.

"It depends on vehicle type, engine type and car design. But keeping tires inflated is one thing that has an effect on fuel economy," he said.

Shankwitz pointed to tire inflation, engine efficiency and aerodynamics as three factors that influence fuel economy. He said speed is the biggest factor by far.

As far as the tire pressure recommendation, "it comes down to the physics of tire," said Shankwitz.

"What happens is that you get more flex in the sidewall," he said.

Essentially, the tire is deforming and reforming as you drive, causing heat and energy to be wasted on that process.

So does 3 percent really matter? According to the U.S. Energy Information Service, Americans use about 20 million barrels of oil every day. Forty-seven percent of that oil goes for gasoline in automobiles, 19 percent goes for diesel fuel. That's a total of 66 percent for fuel.

Slicing that by 3 percent -- which is what would happen if we assume everyone is under-inflated, and then properly inflates -- would result in a savings of 396,000 barrels of oil.

Obviously, not everyone is driving on under-inflated tires. However, if half of us are, and correct the problem, we'd achieve a savings of 198,000 barrels a day. If just one in three people are under-inflated, and corrects that problem, you could achieve a savings of 132,000 barrels a day.

Incidentally, the proposal to increase offshore drilling activity would result in 200,000 additional barrels a day by 2030, according to the Bush Administration.

Shankwitz said you don't have to choose a position on this thing.

"It can be both" drilling and tire inflation, he said.

He suggested checking your tires every two weeks, as newer aluminum tires actually lose more air, more quickly, than older steel tires.

Most cars have a target for inflation on a label inside the driver's door. Or you'll find that in the owner's manual.

 

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