Is it not a good idea to change the oil, filter you have been using... cuz the preious owner took it to walmart each time he changed the oill. They used the cheap filte rand oil. Would it not be a good idea to switch to a dif type of oil/ filter? 6in 87' K5 w/ 35" BFG muds. Kn filter What I need: 4.11 gears, Lim Slip Dif, Force2 Catback, rear springs , Throtle body spacer.