To reach the desired effect, engine oil of your small engine shall be replaced after 25 hours or after one month after its first use, and it shall be replaced every 50 hours or every 3 months afterwards.
1.Preheat the engine for 2-3 minutes and stop the engine. 
Warning: ensure that the sparking plug wire has been disconnected and keep it far away from sparking plug to prevent accidental starting. Clean around the oil filler opening and oil drain cock and prevent dirt and scrap to fall into crankcase (as shown on the right diagram). 
2. Place a can for oil under the engine.
3. Loosen and remove oil drain bolt and drain the engine oil. 
4. Pull the starter by hand for several times to help drain all the residual oil. 
5. Put back the oil drain bolt and tighten it. 

ENGINE OIL RECOMMENDATION
In order to make the engine run ideally, we suggest you to choose MULLER certified speicial engine oil. Usually SAE 10W-30 engine oil is recommended. when your area temperature is among the range shown in the chart, you can use engine oil with other viscosity.