The Beta ratio and filtration ratio are two common rating systems used to designate the abrasive filtration efficiency of fuel filters. Previous research developed a series of wear curves to predict the effects of abrasive particles of varying sizes on fuel injector performance. Based on this data, a formula was generated to predict injector wear based on the number of 5-, 10-, and 15-μm particles in the effluent. This value is called the wear index. (1,2)1Various fuel filters with the same manufacturer rating were evaluated on a test engine to determine the wear index for each of these fuel filters.The results demonstrate the differences between these “similar” fuel filters and how the wear index provides additional information as compared to Beta and filtration ratios.