[The Newell]

Generally, the higher the tire pressure, the better the fuel mileage. In addition to ride comfort, you will also be sacrificing safety by running your tires over the recommended pressure, and the tires will also wear out faster.

The safety aspect comes from the fact that there is less rubber in contact with the road. That means increased braking distance on all surfaces, and also less cornering traction in emergency handling situations.

The tire wear has to do with the fact that the smaller contact patch will mean the center of the tread will wear faster than normal, and the shoulders will wear more slowly. The uneven wear will get you to sub-legal tread in the center in fewer miles. For many this is a red herring, because the tires need to be replaced from age (7 years maximum, generally) long before the tread wears down. (We would generally wear our tires out every four years, give or take.) It becomes very difficult to calculate whether the improved mileage offsets the increased tire wear in lifetime cost-of-operation; obviously, the more expensive fuel is, the more lopsided the equation gets.

Personally, I would not trade the safety off for minor fuel savings