Hydraulic bench stand was constructed at the Transport and Power Machinery Department’s laboratory to conduct four stroke one cylinder air cooled diesel engine F1L511 tests according measurement equipments. The test results indicate that brake mean effective pressures (bmep) higher from 5,2 % the fully loaded (α = 1,3) engine developed when operating on biofuel blends B5, B10 and B20 relative to diesel fuel case. When operating of the fully loaded engine at 1800 and 2600 min-1 speeds, the brake specific fuel consumption lower by, 3,3 % correspondingly, was measured when fuelling the engine with blend B5. Under easy loading conditions, pe ≈ 0,1 MPa, better fuel economy suggested biofuel blend B10. The best brake thermal efficiency at 1800 min-1 and 2600 min-1 speeds was achieved when fuelling the engine with biofuel blend B5 and at intermediate 2200 min-1 speed – with blend B20. In order to have broader view about diesel engine performance efficiency on various biofuel blends long term tests would be necessary.

Raktažodžiai: diesel engine, diesel fuel, rapeseed oil, biofuel blends, performance efficiency