I believe B&S recommend straight 30wt. Personally I would use 10w30 synthetic after initial 5 hr. Break-in on new mower.
What Type Of Oil For Briggs & Stratton 4.5 Hp Lawnmower?
To be honest, I am not into gardening but I decided to start bothering about my yard this year. I have bought a weed eater from trimthatweed.com and it seems to be a good device to make my garden look, at least, nice even thoug I don't have too much time to take proper care of it. Maybe it will be better to hire someone who will do the job.