You need to use a specific type of oil in every riding lawnmower from Husqvarna to prevent engine damage. The oil in a riding lawnmower helps protect against friction and heat as the piston and the crankcase move inside the engine. If these parts don't receive adequate lubrication, the engine will overheat and burn out its seals, ruining a good engine.
All oil used in any Husqvarna engine, including its riding lawnmowers, must meet certain specifications set forth by the American Petroleum Institute, or API. Use only high-quality detergent oils with a service classification of SG-SL. Under most conditions and in temperatures above 00 degrees Celsius, Husqvarna suggests using an oil with an SAE 30 viscosity rating. Husqvarna recommends against using any multi-viscosity oil, such as a 5W30, in these conditions. Multi-viscosity oils will burn quicker in the engine, which can result in poor lubrication and engine damage.
In Colder Weather
There may be certain circumstances in which a multi-viscosity oil is preferable to a regular oil. When the ambient temperature drops below 0 degrees C, Husqvarna suggests using a multi-viscosity oil with a rating of 5W30. This oil allows for easier and quicker starts in colder weather. However, when using this oil, check the oil supply more frequently to monitor the level of oil in the crankcase. If the oil drops below the "Full" line, slowly add 3 to 6 fl. oz. of oil at a time, and recheck the oil level.
Checking the Oil
Husqvarna suggests that you check the oil every time before operating a riding lawnmower. This will allow you to closely monitor the oil supply and register any large drops in oil quantity, which would suggest an oil-burning problem in the engine. Always park the mower on a flat surface before checking the oil level. Remove the oil dipstick from the spout, clean off the tip and reinsert the dipstick. Wait a few moments before pulling it out and checking the oil level.
Changing the Oil
Husqvarna suggests that you change the oil after every 50 hours of operation. This will keep the oil supply fresh and adequately lubricating the crankcase. If you don't operate the mower more than 50 hours during the season, change the oil at least once, preferably at the beginning of the season. Change the oil after the engine has had sufficient time to warm up, which will allow the oil to flow out more freely and remove any built-up gunk that's inside the oil. Replace the oil filter after every 100 hours of operation.