You're two months into the mowing season. Your machines have been logging real hours since spring startup, and the operators who run the tightest shops are already thinking about the next oil service. Not because something's wrong. Because staying ahead of it is what keeps a fleet running clean through August and September instead of limping into fall.
Here's how to get the oil service right: the interval, the oil type, and the two filters that should go with it.
How often should you change the oil in a commercial mower?
Oil changes run on hours, not the calendar. Most commercial engines call for a change every 50 to 100 hours: Briggs Vanguard around 50, Kawasaki and Kohler around 100, with the first change sooner on a new engine (Kawasaki at 25 hours, Kohler at 5). Check the hour meter, not the date.
Here's what that means in peak season. A machine logging 8 to 10 hours a day, five or six days a week, hits 100 hours in about two to three weeks. So a hard-run mower needs its oil changed every few weeks through summer, not once or twice a season. Lighter-use machines stretch further, but the rule is the same: go by the hours.
Change it sooner if you've been on dusty or sandy sites, if the machine sat with old oil over a slow stretch, or if you picked up a used mower and don't know its history.
What type of oil does a commercial lawn mower take?
Most four-cycle commercial mower engines run a 10-weight multi-grade, with the exact spec depending on the engine:
- 10W-30 is the common spec for Kohler Command and many Briggs commercial engines.
- 10W-40 is what Kawasaki recommends for its FR, FS, and FX engines, the ones under a lot of commercial zero-turns.
- SAE 30 straight-weight is fine in warm weather for some engines (common on Briggs above 40°F), but check your manual before running it.
- Synthetic (5W-30, 15W-50, or an engine maker's extended-life synthetic) holds viscosity longer under heat and load and can stretch intervals on high-hour machines.
Always match the weight to your engine maker's spec and your operating temperature. Most of these engines hold around two quarts, so a change doesn't take much oil.
This is for four-cycle mower engines. Two-cycle handheld equipment mixes oil with fuel and is a different job. See our 2-stroke oil guide for that.
The oil service, step by step
Do the whole service in one pass instead of changing oil now and chasing filters later:
- Warm the engine for a few minutes so the oil drains clean.
- Drain the old oil fully. Look at it as it comes out. Metal flake or a burnt smell tells you something.
- Swap the oil filter on schedule while it's drained. Kawasaki calls for a new filter about every 200 hours (every other oil change) and Kohler is similar, but a filter is cheap, so plenty of crews put a fresh one on with every change. Pre-oil the new filter's gasket and spin it on hand-tight.
- Refill with the correct weight to the full mark. Don't overfill.
- Check the air filter while you're in there. A clogged air filter chokes the engine and burns more fuel. If it's gray and loaded, replace it. Full walkthrough in our air filter guide.
- Log the hours or the date so the next service isn't a guess.
That's oil, oil filter, and air filter handled in one stop. Fifteen minutes a machine now beats a rebuild later. Want the oil filter interval broken down by engine brand? Our oil filter change guide covers it.
Where to get the oil and filters for your fleet
Mowmore stocks oil, oil filters, and air filters cross-referenced for the major commercial engine brands, at prices below dealer rates, with same-day or next-day shipping on most orders. Order the service parts for every machine in one cart and get the whole fleet on the same schedule.
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