This paper details an extensive study that was performed to define, quantify, and describe the contaminant found in automotive type transmissions. The results from the study were used to manufacture a new commercially available test contaminant that simulates the contaminant found in high mileage transmissions.The study was undertaken because no commercially available contaminant existed to test transmission related components, especially valves, pumps and filters. Most accepted test contaminants such as AC Fine or Course Test Dust were known not to give representative contaminant related results.The study consisted of collecting 29 oil samples from various mileage vehicles. The particle size distribution, gravimetric level, and chemical composition were found from the samples. Correlation of this data back to the actual materials of manufacture found that four different base stock materials were contributing over 90% (by weight) of the contaminant found in vehicles with 70,000 to 120,000 miles. Manufacturing methods were then defined which reduced these four materials to the same particle size distribution and chemical composition as found from the field. The test contaminant has consequently been named SYNFORM, for SYNthetically FORMulated.The use of this contaminant is finding widespread use to define valve and pump contaminant service life, filter characteristics, and torque convertor contaminant settling by radioactive tracing, among other applications.