Well I picked up a 91 Z24 and it was sitting in a yard for like year to 2 years without running, it had the same oil in it for that long as well and i started it and let it run for like 25 min with that oil, it was full just looked old, now its at my house and i just put new valvoline max life in it and now it was smokeing, now its not smoking from what I see but it smells really (carbony). Do u think its just cleanin itself out or is the motor shot? Amazing enough the motor sounds real strong like theres not tickening or knockin coming from it so what u think?