I used to put some StaBilt in my tank when adding fuel but I switched to Lucas Fuel Conditioner/Stablizer based on suggestions from this forum. Don't know how worthwhile it is because I've not had any real problems with phase shift or water formation. Maybe it's helping and maybe it isn't. I wish someone would come out with an additive to raise the vapor point or boiling point of today's fuel. I've about become convinced that it isn't so much the ethanol in fuel that is the real problem, as much as it's the low vapor point and fuel perculation.
I also use some Octane 130 octane booster in my 12:1 Corvette and my GTX to control pinging. It's real lead, illegal for street use, make your hair fall out and go blind stuff that is only available by mail order by the case and is very pricey. None of the stuff you buy over the counter is even close to it.
I believe in Dupont water pump lubrication additive for the cooling system.
Nothing for
oil as long as a proper
oil for flat tappet cams is used.
But, I'm not any more immune to snake
oil remedies than anyone else.