What type of oil is everyone running? And where does everyone stand on the synthetic/conventional thing? I've heard opinions from both sides of the camp that seem equally as grounded. At my altitude and temperature I've been using 5W30 ('77 350) with no issues. Just your basic NAPA/Wal-Mart conventional. Anyone have any preferred brands for these old trucks? I met somebody that swore by Royal Purple for his Blazer...but he also only changed it every 5 years. Also, what are everyone's opinions on additives? Lucas, STP, etc. I've used that "Keep that engine alive" stuff in the white bottle whenever I remember to buy some. But I don't know enough to say if it's effective or not. A waste? If this discussion already exists, my apologies. Tried using the search function but found zilch.