I would do a couple of oil changes to get the breakin crud out. Amsoil is great oil but a waste in the lawn mower. I have a pos Craftsman mower that is 9 years oil I did a couple of breakin oil changes and put what ever oil I had left over .The motor runs great and the deck has welds where it is cracking "I balance the blade after sharpening" I cut the lawn about 9 months a year once a week and it takes half an hour to do the cutting .I put in some 05w20 Motorcraft this spring and it is still running,I would like a new mower.