Back in the 60's and probably through the 80's we sold a lot of STP here in Texas. It's not an overhaul in a can, but it does slow oil consumption and smoking. In fact there is a good chance if your 216 is a Texas truck, it may well have had STP in it before. My father started selling lubricants in the 30's and I still have the business. I used to sell as much as several cases of STP a day and I have never heard a valid complaint on older engines. Make sure the engine is hot and pour it in slowly while the engine is running. Otherwise it can stay in one blob and stop up your oil pickup. I would not recommend it for newer engines.
