So I went to the Hitching Post today (The dealership where I bought my bike) to get some oil anda filter for my first 600 mile oil change. The manual says to use 20W 40. The parts guy says that yamaha doesn't make yamalube in 20W 40 anymore. He recommended 10W 40. I bought five quarts of it, but I havent put it in yet. I am a mechanic by trade, but I am a professional, and I'm required to put whatever oil a specific machine requires which is recommended by the manufacturer. I don't know a whole lot about different weights of oil, and I don't want to start a huge debate about it, but if somebody out there does know a lot about oil, I'd like to know if the 10W 40 is ok to put in this bike, or should I return it and find what the manual recommends somewhere else? I don't trust parts guys. I've worked as a mechanic at auto dealerships and in fleet operations, and most of them don't know crap about anything. I trust you guys more then that guy.