How to Use Synthetic Oil in a Riding Mower

Read the owner's manual, or contact the manufacturer if you've lost the manual. The manual may state whether your riding mower can use synthetic motor oil. If it does not specifically address synthetic oil, it will state the kind of motor oil you need. As long as a synthetic oil meets the requirements of the recommended oil, it should be safe to use.

Buy the synthetic motor oil. Be sure you purchase the same weight of motor oil that your riding mower manufacturer recommends. Riding lawn mowers typically use 10W-30 or SAE30 motor oil, available at most hardware stores. You should also check how much oil your mower holds so you can purchase the correct amount.

Drain the old motor oil. Each riding mower is different, so you'll have to check the owner's manual for how to drain the oil. Essentially, you must first open the oil fill cap and remove the dipstick, then open the oil drain valve. Use a tube, funnel or other container to drain and catch the oil. Wait until all the oil has drained, and then close the oil drain valve.

Refill the mower with the synthetic oil. Place the funnel into the oil fill tube. Pour the synthetic oil into the funnel slowly so there are no air bubbles. Once all the oil is in, wait a few minutes and then check the oil level with the dipstick. If there is not enough oil, add more and keep checking the level with the dipstick until there is enough. Then place the dipstick in the oil fill tube and seal it by twisting the cap.