My 26 year old small block has started puffing a bit of smoke on start up. Im guessing its valve seals. I also have a bit of a slow rear main leak so I was wondering what you guys have used with success to cure such things. Im already running a thicker oil, but instead of trying 2 or 3 different ones over a few OCI's id like to see what you have to say. I have stayed away from just a high mileage oil cause this engine has a hot flat tappet hydraulic cam and good springs, so it needs ZDDP.