Internal combustion engines are an indispensable part of our daily life, especially in transportation and agriculture sectors. However, the reduction of petroleum resources and environmental problems are leading to an increasing trend towards alternative energy sources. In this regard, hydrogen usage is expected to be a solution for previously mentioned problems as one of the renewable energy resources. In this concept, effects of hydrogen as an additional fuel used in a compression ignition engine performance and exhaust emissions parameters different engine speeds were investigated at full load. For this purpose, a compression ignition engine (CI) with 17/1 compression ratio, four cylinders, four stroke, turbocharger and 3.908 liters engine volume was used. While diesel fuel was injected directly to combustion chamber, hydrogen was added to inlet manifold at rates of 2.5%, 5% and 7.5% as volume. As a result, an increase in engine torque, power, thermal efficiency, nitrogen oxides (NOx) and exhaust gasses temperatures were acquired at every hydrogen addition ratio while a decrease in hydrocarbons (HC), carbon monoxide (CO) and oxygen (O2) emissions were attained. While engine torque exhibited an increase at a rate of 8.3% comparing with standard diesel operation at 1250 min- 1 and 7.5% hydrogen addition ratio, engine power increased 17% at 2250 min- 1 engine speed and 7.5% hydrogen addition ratio. Brake thermal efficiency of 2.5% was obtained as 40.4% comparing with 33% value of SDI at 1750 min- 1. The lowest CO, CO2, HC and NOx emission values were obtained at 2250 min- 1 engine speed and 2.5% hydrogen addition ratio as 0.013; 2500 min- 1 engine speed and 7.5% hydrogen addition ratio as 7.4%; 1250 min- 1 engine speed and 2.5% hydrogen addition ratio as 10 ppm and 1000 min- 1 engine speed and 7.5% hydrogen addition ratio as 1092 ppm respectively comparing with standard diesel operation. © 2013 Elsevier B.V.