The oil on a Murray 3.5HP mower should be changed prior to or at the end of each mowing season. It must also be checked prior to each use to assure the proper oil level. This is a good time to replace the spark plug, clean the air filter and sharpen the blade if needed. The spark plug and the air cleaner are very inexpensive and are necessary to extend the life of the mower. Any auto parts store will carry these parts.
Locate something to sit the front and rear wheel on to raise the mower a few inches. This isn’t absolutely necessary, it just makes it easier to change the oil without having to hold the front of the mower up by hand while the oil drains.
Pull the spark plug wire off the spark plug and bend the wire enough to keep it away from the plug. This eliminates the possibility of the mower attempting to start when the blade is turned. Remove the oil dipstick.
Tip the oil filter-side of the mower up to access the drain plug under the motor. Put down some newspaper and place the drain pan so it will be under the engine drain plug when you lower the mower. Remove the plug with a square hole by inserting the ratchet extension into the hole and turning the drain plug counterclockwise to remove it. Lower the mower so the oil will drain into the pan.
Tip the mower up and install the drain plug, turning it clockwise with the ratchet and extension. Fill the engine with 5W30 non-detergent synthetic oil to the proper level mark on the dipstick. The engine holds 20 ounces of oil when it is completely dry. All the oil will not come out leaving as much as 4 ounces in the engine. Pour 1 quart of oil, which is 16 ounces, in the oil filler tube. Make sure the mower is sitting level for the proper reading on the oil dipstick.
Install the dipstick and pull it out to check the level. Only top it off with a small amount of additional oil and keep checking the dipstick as oil is added to top it off. Screw on the dipstick. Plug the spark plug wire onto the spark plug.
