Don't use any of these but am very familiar with all of them.
Cenpico is a cut above national brands, but doesn't hold up as long as the other two you mention.
Schaeffers is good oil - always been non synthetic until recently added a line of synthetics. I have not tested the synthetics.
Hydrotex was the first and the grand daddy of the specialty lube market. IMHO they are no longer better than others and are overpriced for what you get. Their oil tests comparable with Sheaffers.
All three are rated CI-4 and will work well in CTD, as their primary markets have been Farm Tractors, Truckers and Contruction eguipt. With good filter, and no or light towing - should be able to get 7,500 miles between oil changes with a good filter (My HO).
From your question, I assume you have no interest in synthetics.
Check prices, pick one and enjoy.
Dl5Treez -Where is the copper in the CTD? (not being sarcastic, honest question)