A Basic Service is like a "health check" to keep a running machine going, whereas a Full Service is designed to make a tired machine feel brand new and prevent a mid-summer breakdown.
1. The Basic Service.
This is for mowers that are currently working well but need their annual maintenance to stay under warranty or avoid wear.
Oil Change: Draining the old, black oil and replacing it with fresh SAE 30.
Air Filter Clean: Blowing out dust and debris from the foam or paper element.
Blade Sharpen & Balance: Removing nicks from the blade so it cuts the grass cleanly rather than tearing it.
Spark Plug Clean: Removing carbon deposits and checking the gap.
General Clean: A quick hose-down of the deck.
Safety Check: Ensuring the engine stop-lever works.
2. The Full Service.
This is what you recommend for machines that haven't been touched in years, are hard to start, or are "self-propelled" models with more moving parts.
Everything in the Basic Service, PLUS:
Fuel System Flush: Draining the fuel tank and carburetor bowl to remove "stale" petrol and water contamination (the #1 cause of mower issues).
New Spark Plug: Replacing the plug entirely rather than just cleaning it.
New Air Filter: A brand new filter to ensure the engine "breathes" perfectly.
Drive System Service: (For self-propelled mowers) Removing the rear wheels to grease the gears, checking the drive belt for cracks, and adjusting the cable tension.
Under-Deck Deep Clean: Scraping off all the dried, acidic grass that causes steel decks to rot and rust through.
Cable Lubrication: Oil is dripped down the throttle and brake cables so they don't snap or seize.