The paper provides an analysis of 100% peanut fatty acid methyl esters (FAMEs) and peanut FAME/ULSD#2 blends (P20, P35, and P50) in an indirect injection (IDI) diesel engine (for auxiliary power unit applications) in comparison to ultralow sulfur diesel no. 2 (ULSD#2) at various speeds and 100% load. From the fuel thermal and physical properties, it was determined that up to 50% peanut FAMEs blended with ULSD#2 (P50) would meet the ASTM D6751 fuel standard for viscosity. The ignition delay was in the range of 1 ms, and the apparent heat release presented similar values for all investigated fuels. The maximum cylinder instantaneous gas combustion temperature reached about 2100 K while the total heat flux was 1.95 MW/m(2), and it was found that there was a 7% average increase in brake specific fuel consumption for P50 over ULSD#2. The mechanical efficiency for ULSD#2 and all of the tested FAMEs was around 77%, with 10% loss in overall engine efficiency for FAMEs compared with ULSD#2. Nitrogen oxide (NOx) emissions of the FAMEs, with an average value of 1.8 g/kWh and soot values with an average value of 0.15 g/kWh displayed very similar results with that of ULSD#2. Combustion analysis demonstrated the high tolerance of the IDI engine to various peanut FAME blends with results being similar to ULSD#2 and proved the suitability of this combination of fuel engine for auxiliary power unit applications.