I found this article from the California Air Resources Board.
It contains some very interesting facts about the true costs of underinflation. Some notes from this article, that are absolutely stunning when you consider the affect on fuel consumption:
- NHTSA found that for every 2.96 psi a car or light truck is underinflated, it loses 1% fuel efficiency. For a set of 4 tires, that is 0.74 psi/tire. Not very much, and would probably be difficult to determine with most pressure gauges. If each tire was underinflated by 2.5 psi, which is nothing abnormal and not enough to make the TPMS alarm to come on, the total for the vehicle would be 10 psi, robbing 3.38% from the vehicles fuel efficiency.
- NHTSA found that the average car and light truck in the USA is riding on a set of 4 tires that is underinflated by 10-11 psi. That means a 3-4% decrease in fuel economy.
- NHTSA also found that tires lose 1.78% of their tread life for each 1 psi they are underinflated. So, the average case of 10-11% underinflation yields 17.8% less tire life, according to the article.
Nitrogen tire inflation is a great way to minimize underinflation. Nitrogen filled tires maintain their pressure 4-6 times longer than air filled tires, allowing drivers to stay closer to their recommended tire pressures between service interavals. With the cost of gasoline over $4/gallon in most parts of the country, these wasted dollars can add up to significant losses. Filling tires with nitrogen is a great way to recoup some of these losses.