Although numerous studies have shown the adverse effects of oxidized biodiesel and/or higher total acid number (TAN) and water content in biodiesel fuel on the degradation of fuel delivery materials, limited work has been reported to date to ascertain the presence of these factors under actual engine operation. Therefore, the aim here is to determine if these factors exist under common rail diesel engine (CRDE) operation. For this, an engine test-bed comprising a Toyota IKD-FTV engine coupled to an eddy current dynamometer was operated under two different speed-load test cycles using palm biodiesel with 10.5 h of oxidation stability according to the Rancimat test. The results indicated that the biodiesel fuel samples were not oxidized while both TAN value and water content were unaffected at the end of the CRDE operations under both the test cycles. As such, emphasis should not only be placed solely on the acceleration of fuel delivery materials degradation due to biodiesel oxidation and/or greater TAN value and water content under engine operation. This study also demonstrated that biodiesel conductivity value is a more appropriate indicator of fuel deterioration level under CRDE operation which ultimately determines the compatibility between biodiesel and fuel delivery materials. (C) 2016 Elsevier Ltd. All rights reserved.