Changing the oil and the oil filter on a Troy-Bilt Bronco riding lawn mower is part of the general maintenance on the mower. You should change the oil every 50 hours, which is usually about once a year. Since the Bronco mower does not have a time meter, you need to keep track of how long it takes you to mow the grass and how often you mow. If you don't change the oil, the viscosity of the oil will start to break down, which can cause the engine to overheat and lead to damage to the engine. This procedure should take you about 15 minutes to complete.
Park the Bronco riding mower on a hard, level surface and set the parking brake. Allow the engine to warm up for five minutes, then turn it off.
Open the mower's hood and locate the oil drain valve on the right side of the engine. Pull the plastic cap off the end of the valve to expose the drain port. Remove the dipstick from the oil fill tube. Slide the oil drain hose onto the oil drain port. Place the oil pan at the end of the drain hose, pinch the tabs on the oil drain valve and pull out until oil begins to drain. Allow the oil to drain completely.
Push the end of the oil drain valve until the tabs click into place. Reinstall the plastic cap on the valve. Turn the oil filter counterclockwise by hand until removed. Rub a small amount of oil on the gasket of the new oil filter, using your finger. Turn the oil filter clockwise until the gasket touches the oil filter tray, then twist an additional 1/2 turn.
Slide the funnel into the oil fill tube. Refill the engine with 1-1/2 quarts of new oil, then check the oil level with the dipstick. Add oil until the dipstick reads "Full." Reinsert the dipstick and close the hood.