Function

• Motor oil is used to reduce the amount of friction between the piston and the cylinder. It helps dissipate the heat produced and also cools the sides of the cylinder.
  
  

Types of Oil

• Four stroke engines, those that have a separate oil container, are the most commonly used mower in the United States. These are small engines that require a motor oil with a weight of 5W-30. This is an oil with a thinner viscosity and will not break down as easily as other oils. It flows through the system better. This is the most common form of motor oil used in push mowers.
  
  

Two Stroke Engines

• Two stroke engines differ from four stroke engines in that the oil is not placed into a separate tank on the engine. In two stroke motors, the oil and fuel are actually mixed and then put into the tank. Two stroke engines are common on Lawnboy mowers as well as most gas powered yard trimmers.
  
  

Changing the Oil

• The oil should be changed every 40 hours of use. Motor oil cleans as well as reduces friction. Just remove the oil cap and dump the used oil into a container where it can be taken to a waste material center. Place the mower upright and fill with oil to the prescribed amount. This is not necessary in two stroke models.
  
  

Noticing Issues with Oil

• Always check the oil level when before you start mowing. Check the dipstick for small bits of dirt. If you see dirt, change the motor oil. This grit can cause damage to the motor. Some models come with an oil filter, which should also be changed yearly.