This guide incorporates information from this research, as well as from other industry and government sources.

For Bridgestone tests, we have chosen the Joint TMC/SAE (Society of Automotive Engineers) Fuel Consumption Test Procedure, Type II (SAE J1321). This method produces highly accurate, very repeatable results.

Theory, testing & the real world

One of the most often asked questions is why the results reported in tests – or in manufacturer's advertising – are sometimes so difficult to duplicate in the real world.

Simply put, there are many factors affecting the fuel consumption of a large truck, and most of them interact with each other.

When you run tests, you carefully control as many variables as possible. Speed is rigidly regulated. Idle time is fixed. Drivers, loads, trucks, trailers and test courses remain constant throughout a single test. If the wind blows too hard, if it's too hot or too cold, or if it rains or snows, the test is canceled.

In the real world, you don't have the luxury of controlling everything. One day, you may be hauling a full load of cast iron, the next, a partial load of potato chips. Weather, roads and terrain change constantly.