There are two primary components on a Cub Cadet lawn mower that often wear out after years of service: the mower deck and the engine. The single most important service that extends the life of these components is to keep them clean. Washing the under-belly of the mower deck after each use will prevent corrosion and deterioration. Maintaining fresh engine oil and filters in the engine will likewise prolong the engine's serviceable life. A new engine, regardless of how well it is manufactured, will “wear in” to some extent, generating debris in the engine oil. Likewise, the oil and filter should be replaced at the beginning or end of each mowing season or 100 hours of operation.
Park the mower on a level surface, ideally in an area that allows easy access to the engine and engine oil drain port. Although every effort should be taken to prevent spilling oil onto the ground, park in an area where if a spill does occur, the oil can be quickly and easily cleaned up.
Remove the key from the mower. It’s unlikely the mower will start itself, but it’s better safe than sorry. Also, set the parking brake just in case the Cadet decides to roll.
Drain the engine oil while it is warm. Run the engine at idle speed for several minutes to distribute the oil through the engine, and warm it up so that it flows better when drained. Cold oil flows much like molasses, and leaves dirt and contaminants in the crank case. Warm, freshly circulated engine oil flows more completely and holds dirt and contaminants in suspension. The suspended debris is carried away with the oil as it drains from the engine.
Remove the plastic dust cap from the engine oil drain protruding from the side of the engine. The drain tube is just a straight piece of pipe threaded horizontally into the lowest part of the engine. The cap and valve attached to the end of the drain is normally colored red or yellow on the Cub Cadet to aid in identification.
Place the plastic drain hose onto the end of the oil drain tube. If a drain hose was not provided with the mower, a scrap section of garden hose will work nicely. The hose allows the waste oil to be directed into the oil drain pan, reducing the risk of a spill.
Place a waste oil drain pan under the mower’s engine and route the drain tube into the pan. Take the oil fill/dipstick out of the top of the engine by unscrewing it counter-clockwise. Set it on a clean surface until ready to check the fresh oil fill level.
Turn the fitting at the end of the oil drain tube slightly to the right and push it inward toward the engine, then pull it straight out to open it. The engine oil will now freely drain into the waste oil pan. While the engine oil drains, the engine filter can be removed.
Wipe all the dirt and build-up off of the engine oil filter. The filter is located just above the engine oil drain and is usually colored black. With all the dirt wiped away, wrap the filter with a clean rag to improve grip, and turn it counter-clockwise to unscrew it. The filter still has oil in it, so be careful not to spill the oil while removing the filter. With the filter off, set it in the waste oil drain pan.
Fill the new oil filter with fresh oil as recommended by Cub Cadet. If the recommended oil is unknown, a 5W-30 synthetic engine oil is the perfect substitute. Fill the filter just below the threads, and allow a minute or two for the filter to soak up the oil. Top off the oil in the filter until it again reaches the bottom of the filter threads. Dab a light coat of oil on the filter’s seal with an index finger. This will help ensure a proper seal around the filter when it is reinstalled.
Screw the new filter onto the engine filter threads and tighten it by hand. There is no need to tighten any further than hand tight.
Remove the plastic drain hose. Push the engine oil drain fitting in toward the engine and turn it slightly to the left to lock it in place. Reinstall the plastic dust cap over the drain.
Set a funnel into the engine fill/dipstick port and add 1 quart of oil. Allow the oil a minute or two to settle and insert the dipstick until it bottoms out. Pull it back out and check the level on the dipstick. New oil is hard to see on the stick; angling it just right in the light will allow for the level verification. Continue adding oil a 1/4 quart at a time, checking the level between each fill. Once the fill mark is reached, install the fill/dipstick and screw it into place.
Start and run the engine at idle speed for a few minutes. Kill the engine and re-check the engine oil level. It is common for the oil level to drop a little after the engine has distributed and re-coated the inside with oil. If the level is below the fill mark, top it up again to the fill mark. Make sure not to overfill the engine with oil. Too much oil is as bad, or worse, than too little.