Can sealed lawn mower oil filters be cleaned and reused?

If you are referring to the screw on canister filter, Absolutely not. Change your oil AND filter every 50 hours or one year, whichever comes first. I strongly recommend a quality brand name full synthetic oil in an air cooled engine as the oil temps can reach over 250 degrees on a hot day. It will only cost around 4 dollars more than regular oil. Avoid Fram filters. Use an OEM, Napa Gold (Wix), Purolator Pure One, Walmarts supertech (champion labs) filters, (not their oil as I have 2 quarts of 5w30 SuperTech synthetic and the add pack has separated after 12 months on my shelf).