Daddy used it in his 65 Falcon for YEARS with me telling him he was messin up. He'd just add some when it got time for an oil change instead of changing the oil. I cussed him to myself when I rebuild that engine. I had to chip all the concrete sludge out of that engine with a hammer and chisel. True story. It works well for its intended purposes, but there are WAY better products on the market today.
