Briggs & Stratton, the engine manufacturer for the Troy-Bilt lawnmower model 556, suggest that you change the oil on your new lawn mower after the first five hours of operation. Once the initial oil change is accomplished, change your oil after every 50 hours of engine use or once a year if you do not reach 50 hours every season. Always check your oil before starting your engine each time you mow your lawn.
Start your Troy-Bilt lawnmower and allow it to idle for a few minutes to warm the engine. Warming the engine oil allows it to drain faster and more completely. Stop the engine and pull the black sparkplug wire from the sparkplug at the front of the engine as a safety precaution. Without the wire attached to the sparkplug, the engine cannot start.
Remove the oil fill cap from the top of the engine and clean the area around the opening using a soft cloth. This keeps any dirt and debris from falling back into the oil compartment. Tilt the Troy-Bilt lawnmower, exposing the bottom of the deck and the blades with the air filter side of the mower up. Tilting the mower with the air filter down causes fuel to drain into the air filter and possibly damaging the engine.
Prop the mower with a cement or wood block and place an oil drain pan underneath the mower. Use a 3/8-inch drive socket wrench to remove the drain plug from underneath the deck. Allow the oil to drain completely from the oil compartment. Replace the drain plug, verifying it is tight and remove the block to lower the lawnmower to the ground.
Place a funnel into the oil fill opening and fill the mower with SAE 30 weight motor oil until it reaches the full mark on the dipstick attached to the filler cap. Replace the filler cap and push the sparkplug wire onto the sparkplug.