In decades of real world testing of its own and competitors' tires, Bridgestone has found fleets generally will not achieve long-term fuel economy improvements equal to those found in carefully controlled short-term tests.

Bridgestone engineers suggest that any fuel economy method that does not produce at least a 2-percent improvement in controlled testing will probably not produce any measurable real-world effect in the long term.

Whatever the size of the test results, you generally see only about half of it in the real world. As we mentioned before, much of this is because of interference by other factors outside the controlled variables of scientific testing.

Of course, you should always try to save fuel. It can save you money, while reducing both pollution and our dependence on foreign oil. But don't expect to get much more than half the effect you find in a test.