Why You Should Clean Your Mower Deck (And How to Do It)

When was the last time you looked under your mower deck? If it's been a while, you might be surprised at the inches of caked-on grass packed underneath. This buildup isn't just ugly — it's actively hurting your mower's performance.

Caked grass reduces cut quality. The deck is designed with specific airflow channels that lift grass and direct clippings. When those channels are packed with old clippings, airflow is restricted and your cut quality drops. Grass lays over instead of standing up for a clean cut.

It causes rust. Grass holds moisture against the metal deck. Over time, this causes rust that weakens the deck. We've seen decks rusted through from chronic grass buildup — and deck replacement is expensive.

It makes the engine work harder. When the blade has to push through packed grass debris, the engine works harder, burns more fuel, and creates more wear. It's like trying to run through knee-deep mud instead of on a clear path.

How to clean it: tip the mower on its side (air filter side up for push mowers — this prevents oil from flooding the air filter). Use a putty knife, paint scraper, or deck scraping tool to remove the caked grass. A wire brush helps with stubborn spots. Spray with a hose if needed, then let it dry completely.

How often? Ideally, give the deck a quick scrape every few mowings. At minimum, do a thorough cleaning at the start and end of each season.

Prevention tip: spray the clean deck with a silicone-based lubricant, cooking spray, or dedicated deck coating product. This makes grass less likely to stick. Reapply every few mowings.

For riding mower decks, the process is the same but you'll need to get the deck off or use a jack to access the underside. Some people install deck washout ports — you connect a garden hose and let water spray under the deck while the blade spins. These work reasonably well for regular maintenance but don't replace a good manual scraping periodically.