i need to find a tech manual for a murray so i know whether i need to add oil to the gas when it's added, i used to have a mower when i was a kid that this was the case with and i'm not seeing anywhere else on the mower where there's a place to add oil. model number 20303x40. i can't find it on their website. would appreciate either somewhere i can find the answer, the manual, or maybe both, doesn't really matter. thanks everybody