im gonna help my buddy to a tuneup on his truck before he gets it smogged. its a 96 1/2t chevy w/ a 305. 180k on the engine. im thinking oil change, plugs,air filter. what weight of oil would be best? would a thicker oil be better for emissions? 10-30, 10-40? fill with 87 or 91? i think the cheap stuff would be better since it burns more completely in a stocker. opinions? any snake oils for the fuel to help pass? i seem to remember hearing someone on here using a fuel additive with good results. anything else i should do?