Anyone got any advice on some additives to help clean out the injectors, or fuel lines, anything I can just add to the tank and let it do its thing?

I have never done any injector maintenance or have never added anything special to the fuel to clean out the system. Any stuff anyone would recommend to do a quick cleaning, even if not as thorough as it would be taking it apart?

Ive been driving it for 6 years now with a dual tank greasecar system.

Also what kind of oil would one recommend for for the 85 300TD in the midst of a freezing Quebec winter.?