I just got my hands on an 8yr old Craftsman walk-behind (917.388751) with a 6.5hp B&S motor (123K02-0181-E1). The previous owner said that he never did an oil change before and only added oil when it got low. I can start it on the first pull, however the engine sounds like it is running slower than other mowers I have used. It seems to cut grass ok though. There is direct speed adjustment, the manual just says it is preset. I plan to change the oil, put in fresh gas, and change the air filter and spark plug. Is there anything else that would be recommended? Should I get some of those oil additives that claim to "clean" the engine? or try to clean out some other parts like the carb? Or is there pretty much nothing I should do at this point? Thanks.