The present experimental study aims to find the effect of the nozzle opening pressure (NOP) on the behaviour of a single cylinder, direct injection, compression ignition engine, run on a non-petroleum fuel; i.e. JMETPO20 blend, which contains 80% jatropha methyl ester and 20% tyre pyrolysis oil on a volume basis. In order to find an optimum NOP for the blend, tests were conducted at an optimized injection timing with five different NOPs viz. 210, 220, 230, 240 and 250 bar in addition to the original NOP of 200 bar, and the findings were matched with those of diesel operation. The combustion parameters were analysed for the blend and test results showed that the peak cylinder pressure and maximum heat release rate were marginally increased at the NOP of 220 bar in comparison to the original NOP of 200 bar at full load. Further, it was found from the results that for the blend with the NOP of 220 bar, the brake thermal efficiency increased by about 5.12%, while the smoke opacity, brake specific carbon monoxide, and hydrocarbon emissions were decreased by about 9.5%, 1.57% and 6.26% respectively when compared to those of the original operating condition at full load. (C) 2017 Elsevier Ltd. All rights reserved.