Gassing up your car is about to take on a new meaning.Fill your tires with pure nitrogen and you’ll get better gas mileage, advocates of the practice say. Your tires will be safer, and they’ll last longer.A colorless, odorless, tasteless gas that makes up about 78 percent of the Earth’s atmosphere, nitrogen could cost you as much as $10 a tire. But what you save on gas, tire replacement and peace of mind will make up the difference, according to the pitch.Already, retailers like Costco and Olin Mott stores offer nitrogen, and Pep Boys has test-marketed it.Starting Saturday, buyers of all new cars sold at select Crown dealerships in the Tampa Bay area will find their tires filled with nitrogen. Eventually, all 13 dealerships will offer it.The thinking is that nitrogen’s larger molecules prevent it from seeping out of a tire as quickly as air. So inflating tires with nearly pure nitrogen – which has been done for years in race cars, commercial airliners and long-distance trucks – allows them to retain correct pressure longer. News source: SP Times Pressure is vital because a properly inflated tire is a safer, more efficient tire. The National Highway Traffic Safety Administration says most drivers can improve gas mileage by nearly 3 percent by keeping their vehicle tires within the recommended pressure range. The government also estimates the nation loses more than 2 million gallons of gas every day due to underinflated tires.Enter nitrogen. Chemical No. 7 on your periodic chart of the elements. At anywhere from $2 to $10 per tire.Besides attracting customers and addressing safety concerns, it’s a way to fight inflation. Or rather, the lack of it, said Jim Myers, Crown’s chief operating officer.”The whole theory is that air bleeds through the tire slowly,” Myers said. “And if someone isn’t diligent, any tire will lose air over time. But because of nitrogen’s properties, that doesn’t happen as quickly.”Myers said Crown will also offer to replace air with nitrogen on any vehicle for $39.What happens if tire pressure drops and the driver is not near a garage or tire store that sells nitrogen?Topping off with compressed air won’t hurt, tire experts say, and the tire can be purged and refilled with nitrogen later.So should motorists feel … pressured to put nitrogen in their tires?”It sounds like it has mostly positive points,” said Randy Bly, director of community relations for AAA Auto Club South in Tampa. “Nitrogen helps keep tires cooler under open highway conditions, and it’s less likely to leak out, so that would help with fuel mileage.”The only negative would be the cost. But it may well be worth it.”Nitrogen-filled tires stay inflated about three times as long as than air-filled tires, advocates say, and while a typical tire inflated with compressed air might lose 2.7 pounds of pressure monthly, one filled with nitrogen loses 0.7 pound.But Jim Davis, public relations manager for Goodyear Tire and Rubber, says replacing air with nitrogen is “a tough call.””The objective is to have the correct air pressure,” Davis said. “And over time, minute amounts of air do leak out.”There is no harm to the tire from using regular air. But we urge people to check their tires monthly.”What happens, Davis said, is that decreased air pressure flattens a tire, creating more surface area between the tire and the road. That added friction can make the engine work harder and cause tires to overheat, possibly leading to a blowout.”More tire surface means it takes more power to roll that tire,” Davis said. “A correctly inflated tire is going to roll more easily.”Checking tires for correct pressure also has a side benefit.”When you’re down there, look at the tires,” Davis said. “You may notice a nail or tread that is wearing abnormally, and you can catch it before the problem becomes worse.”At least one tire manufacturer is even more skeptical about the advantages of nitrogen in the family car.Michelin officials recommend nitrogen only for tires used “in a high risk environment and/or when the user wants to reduce the consequences of a potential abnormal overheating of the tire-wheel assembly (for example in some aircraft applications),” according to a company statement.But for all other tires in normal use, nitrogen “is not required and does not necessarily bring the expected benefit.”It is true that the physical properties of nitrogen reduce the pressure loss due to the natural permeability of the materials of the tire and thus the broad use of nitrogen will in general assist motorists with pressure maintenance.”Nevertheless, the existence of several other possible sources of leaks (tire/rim interface, valve, valve/rim interface and the wheel) prevents the guarantee of better pressure maintenance for individuals using nitrogen inflation.”So we can save the expense if we just check our tires regularly.The trouble is, we don’t.As recently as two years ago, government and tire industry surveys showed close to 30 percent of cars, vans, pickups and SUVs on the road had at least one tire that was substantially underinflated, at least 8 psi below the recommended minimum pressure.But high gas prices and consumer education may be cutting into that number. According to a survey by Uniroyal Tire in mid August, nearly 50 percent of Americans said they are now checking the air pressure in their tires once a month.Still, that leaves millions of unchecked tires.”Most people don’t take care of their tires on a regular basis,” said Dave Zielasko, editor and publisher of Tire Business , an Akron, Ohio, trade publication. “Tires are one of the most underappreciated part of the vehicle. People take them for granted. But the reality is they do need to be checked.”Remember, it’s the only part of the vehicle that touches the road.”