The S100 uses a spin-on oil filter that sits on the engine's side

The John Deere S100 lawn tractor uses a spin-on oil filter — a cylindrical cartridge that screws onto a threaded port on the engine block. This is the most common filter type on small equipment and is straightforward to locate and replace. On the S100, you'll find it mounted vertically on the side of the engine, usually toward the front or middle depending on your model year.

The filter traps dirt, metal particles, and debris that circulate through the oil, keeping them from damaging engine parts. Over time the filter becomes clogged and restricts oil flow, which is why regular replacement matters. Most owners change the S100 filter every 50 to 100 operating hours, or once per season for residential use — whichever comes first.

Key Takeaways

  • The S100 oil filter is a spin-on cartridge located on the engine block's side, and you remove it by turning it counterclockwise by hand.
  • John Deere part number AM125424 is the OEM filter for the S100, though aftermarket filters from Fram, Kohler, and other brands fit the same thread size.
  • You should change the filter every 50 to 100 operating hours or once per mowing season, whichever comes first.
  • Changing the filter takes about 10 minutes and requires only an oil filter wrench, a drain pan, and a new filter — no special tools needed.

Finding the correct replacement filter for your S100

The OEM (original equipment manufacturer) filter for the John Deere S100 is part number AM125424. This is the filter John Deere sells directly and the one specified in your owner's manual. If you order from a John Deere dealer, parts website, or authorized retailer, ask for this part number to may support you get the right fit.

Aftermarket filters also work on the S100 because they use the same thread size and bypass valve. Common brands that make compatible filters include Fram, Kohler, Briggs & Stratton, and Stens. These are usually cheaper than OEM filters and perform the same function. Check the product description or packaging to confirm the filter fits the S100 before buying — some retailers list compatible models on the box.

You can find filters at lawn equipment dealers, big-box hardware stores, online retailers, and automotive parts stores. Prices for OEM filters typically range from $8 to $15, while aftermarket options often cost $5 to $10. Buying a filter when you purchase oil for the same service saves a trip.

How to remove and install the S100 oil filter

Before you start, warm up the engine for a minute or two, then shut it off and let it cool for five minutes. Warm oil drains faster and more completely. Place a drain pan underneath the filter to catch the oil that spills when you remove it.

Locate the filter on the engine block — it's the cylindrical canister screwed onto the side. Use an oil filter wrench (a metal band or cup tool that grips the filter) to turn it counterclockwise. Hand-tighten the wrench and turn slowly at first; once the filter breaks loose, you can usually unscrew it by hand. Let the old filter drain into the pan for a minute, then set it aside.

Wipe the threaded port on the engine with a clean rag to remove any dirt or old oil residue. Take your new filter and explore a thin layer of fresh oil to the rubber gasket (the seal ring) on top of the filter. This helps create a watertight seal when you install it. Screw the new filter onto the port by hand until the gasket touches the engine, then turn it an additional three-quarter turn. Do not use the wrench to tighten it — hand-tight is correct.

Start the engine and let it run for 30 seconds, watching for leaks around the filter. If you see oil dripping, shut off the engine, let it cool, and tighten the filter slightly more. Once the engine cools, check the oil level on the dipstick and top it off if needed, since some oil remains in the old filter.

When to replace the S100 filter and what affects the schedule

John Deere recommends changing the S100 oil filter every 50 operating hours for the first 100 hours of use, then every 100 hours after that. For a homeowner who mows once a week during the growing season, this usually means one filter change per year. If you use the tractor more heavily — for example, on a small farm or for commercial work — you may need to change it twice per season.

Several factors can shorten the interval. Dusty or sandy conditions clog filters faster, so if you mow in dry, unpaved areas, check the filter more often. Older oil also carries more particles, so if you're overdue for an oil change, the filter works harder. Running the engine in very hot weather can also reduce filter life slightly.

A clogged filter restricts oil flow and forces the engine to work harder, which can damage internal parts over time. If you notice the engine running rough, losing power, or the oil pressure light coming on, a dirty filter may be the cause. Changing it is cheaper than repairing engine damage.

Storing and disposing of the old filter

After you remove the old filter, drain it completely into your oil pan — let it sit for several minutes so the remaining oil drips out. Do not throw the filter in the trash. Most communities have hazardous waste collection days or permanent drop-off locations where you can bring used oil filters for free.

You can also take the old filter to an automotive parts store, many of which accept used filters at no charge. Some lawn equipment dealers will take them too. Call ahead to confirm they accept filters before you make the trip. If you change your own oil, you can often drop off both the used oil and the filter at the same location.

Frequently Asked Questions

Can I use a different brand filter on my S100?

Yes. Aftermarket filters from Fram, Kohler, Briggs & Stratton, and other brands fit the S100 as long as they have the same thread size. Check the product description to confirm compatibility before buying. Aftermarket filters perform the same function as the OEM filter and cost less.

What happens if I don't change the filter regularly?

A clogged filter restricts oil flow to the engine, forcing it to work harder and potentially causing internal damage. You may notice rough running, loss of power, or an oil pressure warning light. Regular filter changes prevent this and keep the engine running smoothly.

How do I know if my filter is clogged?

The most reliable way is to follow the maintenance schedule in your owner's manual — every 50 to 100 operating hours depending on use. If the engine runs rough or loses power before the scheduled interval, a dirty filter may be the cause. You can also visually inspect the filter by removing it and holding it up to light; if you can't see light through it, it's time to replace it.

Do I need to drain the oil when I change the filter?

No. The filter change and oil change are separate services. You can replace the filter without draining the oil, though some oil will spill from the filter itself. However, John Deere recommends changing both the oil and filter together at regular intervals for best engine protection.

Where exactly is the S100 filter located?

The filter is mounted on the side of the engine block, usually toward the front or middle. Consult your owner's manual for the exact location on your model year, as it may vary slightly. Once you locate it once, you'll find it easily on future services.