Due to recent legislation on CO2 emissions, Heavy Duty OEM’s and their suppliers have had an increased interest in improving vehicle fuel economy. Many aspects are being investigated including vehicle aerodynamics, tire rolling resistance, waste heat recovery, engine fuel efficiency, and many others. Crankcase lubricants offer a cost-effective mechanism to reduce engine friction and increase engine fuel efficiency. The potential gains realized by optimized fuel-efficient lubricants are relatively small, on the order of 1-3%. Therefore, in order to develop these lubricants, formulators must have a robust, repeatable, and realistic test method for differentiation. To address this need, Intertek has been involved with developing fuel economy tests for many years, starting with what became the Sequence VI test for passenger car lubricants in the early 1990’s. Most recently, Intertek has helped develop different FE programs to support the MD and HD diesel industry. Examples of engine platforms include: Cummins 15L ISX, Ford 6.7L, CAT C15, Mack MP8, and Cummins 5.9L. Realizing small improvements in fuel consumption requires attention to detail in the set-up and execution of the test procedure in order to report results with confidence. This paper discusses some of the key ingredients to a repeatable test procedure, including instrumentation, control, cycle design, and specific engine effects. Often times, the most challenging variable is the engine itself.