2013 40hp 4 stroke Mercury 3cyl. It usually gets about 60/70 hrs running time a year, probably 40 of it trolling. I use Mercury 4 stroke synthetic oil and change oil & filter every year about this time. It uses no oil and runs great. Last year because of our drought I only put around 20/25 hrs total on it. The oil still looks to be clean as new. Any reason to change it or should it be good for another year.