What You Need to Know Before Starting
Regular oil changes are one of the most important maintenance tasks for keeping your riding lawn mower engine healthy and extending its lifespan. Old oil breaks down over time, loses its ability to lubricate engine components, and accumulates dirt and debris that can damage internal parts. Most manufacturers recommend changing your mower’s oil every 50–100 hours of operation or at least once per year, whichever comes first.
Safety is essential before you begin. Always disconnect the spark plug wire to prevent accidental starting. Never work on a hot engine—let it cool for at least 15 minutes after the last use. Wear gloves to protect your hands from sharp edges and hot metal. Position your mower on level ground and engage the parking brake to prevent rolling.
Consult your owner’s manual to locate the exact specifications for your model. You’ll need to know the correct oil type (SAE grade), total capacity in ounces, the drain plug location, and whether your model includes an oil filter. Different engines—Briggs & Stratton, Kohler, Tecumseh—may have slightly different layouts, so manufacturer guidance is invaluable.
Gathering the Right Materials and Tools
Before you start, assemble everything you’ll need to avoid mid-task trips for missing items:
- Oil: Purchase the SAE grade specified in your manual. Most small engines use 10W-30 or 5W-30, suitable for a range of temperatures. Check whether your manual recommends synthetic or conventional oil—some newer engines perform better with synthetic, while others run fine on conventional. Typical capacity is 48–64 ounces.
- Oil drain pan: A shallow metal or plastic pan to catch old oil. A 5-quart capacity is sufficient for most mowers.
- Wrench: Usually a combination wrench (often 5/8 inch or 3/4 inch) to remove the drain plug. Check your manual for the exact size.
- Oil filter wrench (if applicable): A strap wrench or socket-style filter wrench to remove the oil filter. Not all riding mowers have oil filters; check your manual.
- Oil filter (if applicable): Purchase the exact replacement filter for your engine model.
- Rags or shop towels: For cleaning spills and wiping components.
- Dipstick or sight gauge: Most mowers have a built-in dipstick for checking oil level; verify this with your manual.
- Oil disposal container: Used oil must be disposed of properly. Many auto parts stores, service stations, and municipal hazardous waste centers accept used oil for free.
Important note on oil disposal: Never pour used oil into the ground, storm drains, or trash. Used motor oil is a hazardous material that contaminates soil and water. Most communities have established collection points, and many retailers that sell oil accept used oil at no charge.
Step-by-Step Oil Change Process
1. Prepare the Mower
Start by parking your mower on a level surface. Engage the parking brake and disconnect the spark plug wire from the spark plug by gently twisting and pulling. This prevents accidental engine start while you work. Allow the engine to cool for 15–20 minutes if it has run recently—warm oil drains more completely, but hot oil can cause burns.
For easier draining, you can warm the engine slightly by running it for 30 seconds to 1 minute. This thins the oil so it flows out more completely, leaving less residue in the pan. Stop the engine and disconnect the spark plug wire before proceeding.
2. Locate and Access the Drain Plug
The oil drain plug is typically located on the lowest part of the engine or mounted on the underside of the engine block. On some mowers, you may need to tilt the mower on its side or remove the mower deck slightly to access it comfortably. Consult your manual for the exact location and any special removal instructions.
Slide your oil drain pan directly beneath the drain plug. Some mowers have tight spaces, so position the pan carefully to catch all oil as it drains.
3. Drain the Oil
Using your wrench, carefully loosen the drain plug by turning it counterclockwise. Once it is hand-tight, carefully unscrew it the rest of the way by hand, allowing the oil to flow into the drain pan. If the plug is hot, use a rag to protect your hand. Set the drain plug aside on a clean rag—you will reinstall it later.
Allow 5–10 minutes for the oil to drain completely. Tilt the engine slightly if possible to direct any remaining oil toward the drain pan. The oil flow will slow to occasional drips when most of the oil has drained.
4. Replace the Oil Filter (If Equipped)
Not all riding mowers have oil filters. Check your manual to determine if your model includes one. If it does, the filter is typically mounted on the side or top of the engine block.
Position your drain pan beneath the filter to catch residual oil. Using an oil filter wrench, turn the filter counterclockwise to loosen it. Once loose, carefully unscrew it by hand. A small amount of oil will spill, so keep the drain pan in place.
Before installing the new filter, wipe the filter mounting surface clean with a rag to remove any old gasket material or debris. Apply a thin layer of new oil to the rubber gasket of the replacement filter (this helps create a proper seal). Screw the new filter onto the mounting by hand until the gasket contacts the surface, then tighten it an additional three-quarter turn. Do not over-tighten, as this can damage the filter or make removal difficult next time.
5. Reinstall the Drain Plug
Wipe the drain plug clean with a rag and inspect its threads for damage. If the plug or hole is stripped, you may need a replacement plug kit or professional service. For a normal plug, carefully thread it by hand into the drain hole to avoid cross-threading, then tighten it with your wrench. Most drain plugs require moderate tightness—snug enough to prevent leaks but not so tight that you strip the threads. If you’re unsure of the correct torque, consult your manual.
6. Refill the Engine with New Oil
Locate the oil fill cap on top of the engine (usually marked with an oil can symbol). Unscrew and remove it. Place a funnel in the opening to prevent spills. Slowly pour the new oil into the engine, stopping periodically to check the level with the dipstick.
To check the level accurately, remove the dipstick, wipe it clean on a rag, reinsert it fully, remove it again, and observe the oil level. The mark should reach the full line or be near the upper limit. Most mowers require between 48 and 64 ounces, but refer to your manual for the exact capacity.
Once the level is correct, reinstall the oil fill cap and tighten it firmly.
7. Verify Proper Operation
Reconnect the spark plug wire to the spark plug by pushing it firmly onto the connector. Start the engine and let it run at idle for 1–2 minutes. This circulates the new oil through the engine and allows you to check for leaks.
Watch the drain plug area and filter (if equipped) for any signs of leaking oil. If you notice a leak, stop the engine immediately, disconnect the spark plug wire, and tighten the drain plug or filter as needed. After the engine cools, check the oil level again with the dipstick and top up if necessary.
Common Variations by Engine Type
Briggs & Stratton Engines: These are the most common engines on residential riding mowers. Most Briggs & Stratton models do not include an oil filter; instead, they use a foam air filter element that filters oil mist. Oil change procedures are straightforward—simply drain and refill. The drain plug is typically located on the side of the engine crankcase. Oil capacity ranges from 48 to 64 ounces depending on model size.
Kohler Engines: Kohler engines, found on many premium mowers, often include cartridge-style oil filters. Access to these filters varies by model; some are located on top of the engine (easy to reach), while others are positioned to the side or underneath (requiring mower tilt). Kohler engines often specify synthetic oil for improved performance, so check your manual. Typical oil capacity is 56–64 ounces.
Tecumseh Engines: Older riding mowers may use Tecumseh engines. These typically lack oil filters and have drain plugs located on the bottom of the crankcase. Oil capacity is generally 48–56 ounces. Because these are older engines, finding replacement parts can be challenging; consult a small engine specialist if you encounter issues.
Drain Plug Accessibility: Some mower designs position the drain plug in difficult-to-reach locations. If your mower’s drain plug is hard to access, tilting the mower on its side (following manufacturer guidance) can help. Never tilt toward the carburetor side, as this can cause fuel to drain into the oil.
Troubleshooting and Post-Change Checks
Oil Level Too Low After Refilling: If the dipstick shows low oil after you’ve added the specified capacity, the engine may be burning oil or have an internal leak. Add a small amount more oil and recheck. If the level remains low after several hours of operation, have a small engine technician inspect the engine for wear or damage.
Oil Leaking After an Oil Change: Leaks commonly result from an under-tightened drain plug, over-tightened or improperly seated oil filter, or cross-threaded drain plug. Turn off the engine, disconnect the spark plug wire, and wait for the engine to cool. Inspect the drain plug and filter, tighten as needed, and recheck after running the engine. If leaking persists, have a professional inspect for damaged threads or internal seal problems.
Engine Runs Rough or Smokes: If the engine seems to run poorly or produces excessive smoke after an oil change, you may have added the wrong oil type (check the SAE grade on the bottle against your manual) or overfilled the crankcase. Allow the engine to cool and check the dipstick. If overfilled, drain excess oil into your drain pan until the level is correct.
Used Oil Disposal: Store used oil in a sealed container away from heat and children. Most auto parts retailers (AutoZone, O’Reilly, Jiffy Lube), service stations, and municipal hazardous waste facilities accept used oil at no charge. Some communities offer collection days for household hazardous waste.
Maintenance Schedule and Best Practices
Beyond regular oil changes, maintain your mower’s engine health by checking oil level at the start of each mowing season and every 5–10 hours of operation during the season. Keep the engine air filter clean or replaced as needed—a clogged air filter restricts oxygen to the engine and increases wear.
Use quality oil appropriate for your climate. Cold-weather regions benefit from 5W-30 oil, which flows freely in low temperatures. Warmer regions can use 10W-30 or even 10W-40 oil. Always follow your manual’s recommendations for oil type.
If your mower is stored for the winter, consider changing the oil before storage to remove contaminants that accumulate during the season. Fresh oil helps protect engine components during months of inactivity.
Frequently Asked Questions
How often should I change the oil in my riding mower?
Most manufacturers recommend an oil change every 50–100 hours of operation or at least once per year, whichever comes first. If you mow frequently (2–3 times per week), you may reach 50 hours in a single season. Casual mowers might need an oil change only annually. Check your manual for model-specific guidance, and consider more frequent changes if your mower operates in dusty conditions.
Can I use the same oil I use in my car in my riding mower?
Not always. While some car oils and mower oils share SAE grades (like 10W-30), automotive oils often contain detergents and additives unsuitable for small engines. Small engines run hotter and have less sophisticated cooling systems, so they require oil formulated specifically for them. Always use oil labeled for small engines, lawn mowers, or motorcycles. Check your manual to confirm the correct product.
What if my riding mower doesn’t have an oil drain plug?
A small number of older or budget mowers use a cartridge-style oil filter that serves as the drain point, or they may have a removable oil pan beneath the engine. Consult your manual for the exact oil change procedure. If you cannot locate a drain plug, contact the manufacturer or a local small engine repair shop for guidance specific to your model.
Do I need to change the oil filter every time I change the oil?
If your mower has an oil filter, it is best practice to replace it during every oil change. An old filter can become clogged, reducing oil flow and increasing engine wear. However, if your manual specifies changing the filter every other oil change, follow that guidance. Check your owner’s manual for your mower’s recommended service intervals.
