A Technique to Determine Fuel Economy Points to Areas for Improvement: A test to evaluate fuel economy of a vehicle generally involves measurement of fuel consumption and the force to drive the vehicle on a chassis dynamometer. Also, the engine alone is operated on an engine dynamometer to measure fuel consumption. Since these two tests are performed independently, it is difficult to determine how effectively design improvements in the engine improve overall vehicle fuel economy. Thus, more information than just conventional fuel economy data should be acquired when a vehicle is tested to evaluate fuel economy. Consequently, engineers at Fuji Heavy Industries developed a method that produces information to help evaluate engine performance and vehicle performance to determine which source consumes more fuel than other sources. The chapter consists of 9 pages including 9 figures.