Test #4: Low Tire Pressure vs. Properly Inflated Tires
Test #4: Low Tire Pressure vs. Properly Inflated Tires
Result: Important for many reasons
No matter how many times drivers hear that tire pressure is important they hate checking it. Probably because they don't like squatting beside their car in a busy gas station with fumes swirling around them. But it is important, for a number of reasons Properly inflated tires are less likely to fail at high speeds. They wear more evenly and, yes, they deliver better gas mileage. How much? In this test we saw a modest but noticeable difference. It might have been more dramatic if the test was conducted at a lower temperature; it was 108 degrees Fahrenheit the day we did our tests.
Method: We drove two loops at about 60 mph. Once, the tires were 5 psi below the pressure recommended by the manufacturer. The second time, the tires were about 2 psi above the recommended around. We overinflated the tires because it's difficult to get a reliable inflation level when the tires are already warmed up. We felt that it was important to make sure the tires were inflated to the recommended level or slightly above. Furthermore, tires are constructed to allow for a certain amount of overinflation, though they will then deliver a harsher ride.
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Land Rover
Underinflated tires 20.5 mpg
Properly inflated tires 21.4 mpg
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Percent change 4.4 percent improvement
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Mustang
Underinflated tires 23.7 mpg
Properly inflated tires 23.7 mpg
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Percent change 0 percent improvement *
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* We felt that because of the high temperatures the tires were never sufficiently underinflated enough to show a difference. Even though we deflated them by 5 psi when cold, the high temperature brought them back up to the required inflation level.
Result: Important for many reasons
No matter how many times drivers hear that tire pressure is important they hate checking it. Probably because they don't like squatting beside their car in a busy gas station with fumes swirling around them. But it is important, for a number of reasons Properly inflated tires are less likely to fail at high speeds. They wear more evenly and, yes, they deliver better gas mileage. How much? In this test we saw a modest but noticeable difference. It might have been more dramatic if the test was conducted at a lower temperature; it was 108 degrees Fahrenheit the day we did our tests.
Method: We drove two loops at about 60 mph. Once, the tires were 5 psi below the pressure recommended by the manufacturer. The second time, the tires were about 2 psi above the recommended around. We overinflated the tires because it's difficult to get a reliable inflation level when the tires are already warmed up. We felt that it was important to make sure the tires were inflated to the recommended level or slightly above. Furthermore, tires are constructed to allow for a certain amount of overinflation, though they will then deliver a harsher ride.
_______________________________________
Land Rover
Underinflated tires 20.5 mpg
Properly inflated tires 21.4 mpg
_______________________________________
Percent change 4.4 percent improvement
_______________________________________
Mustang
Underinflated tires 23.7 mpg
Properly inflated tires 23.7 mpg
_______________________________________
Percent change 0 percent improvement *
_______________________________________
* We felt that because of the high temperatures the tires were never sufficiently underinflated enough to show a difference. Even though we deflated them by 5 psi when cold, the high temperature brought them back up to the required inflation level.