Eleven years ago I bought a used Honda lawn mower that the oringinal owner had for two years(went to a bigger model). He only changed the motor oil once when he had it. I only add oil when it needs it. I use Napa single HD 30 weight. It has been used four to six times a month for the last eleven years. I mow one acre property(keeps my weight down). Honda builds a heck of a motor. I was thinking of changing the oil at end of season. Thinking of using Mobil 1...think it is worth it? Or just keep using the .99 cent Napa stuff?