Abstract: The influences of load and temperature on tribological properties of soot contaminated engine oil was investigated by using ball-disc reciprocating mode on the SRV IV oscillating reciprocating friction and wear tester. With the assistance of scanning electron microscopy/energy-dispersive spectrometry, 3D surface profilometer and Raman, the worn steel surfaces under lubrication of soot contaminated engine oil at several loads and temperatures were analyzed. Results indicate that for lubricating oil with 5% diesel soot, " friction coefficient spike” was found when either load or temperature increased and it produced locally high wear. The rupture of oil film and starvation of lubricating oil at tribo-interface were induced by variations in temperature and load.