In an open road test conducted by Popular Mechanics, it was determined that there was only a gas mileage savings of .005 mpg between a car running with high pressure in the tires and normal pressure in the tires. According to Popular Mechanics, the savings in gas mileage was not worth the trade-off in the poor handling of the vehicle with too much air pressure in the tires.
Benefits of Proper Tire Pressure
Keeping the proper amount of air pressure in tires can provide a mileage increase of 3-4 percent over tires that have low tire pressure. For this reason, it is important to keep all of the vehicle's tires inflated to the manufacturer's specifications for the tire.
High-tire pressure tires may increase gas mileage by a percent or two but the dangers involved could negate the savings seen at the gas pump. Tires that have high tire pressure will have less tread touching the ground, could cause the vehicle to vibrate at a dangerous level, and therefore make it harder to keep the vehicle safely on the road.
Low Tire Pressure
Driving a vehicle with low-tire pressure will cause the tires to spread out on the ground and therefore decrease the vehicle's gas mileage by as much as 6 percent. Low-tire pressure can also make the vehicle harder to handle on the road.
Determining the correct tire pressure for tires
All vehicles have tire size and pressure charts located in the vehicle somewhere. The charts can be found on the driver's door jam, in the glove box or in the owner's handbook. According to Fueleconomy.gov, a person should never put air in a tire based on the maximum air pressure that is printed on the sidewall of the tire. If the tire size and pressure charts are not handy, then inflate the tires to where they are at the point of even wear against the ground.
Proper tire pressure is one of many factors in getting the best gas mileage from a vehicle. Other factors that gauge gas mileage are excess weight in the vehicle, weather conditions and the driver's driving style.