You are right about all the above - but you need to use a 50/50 mixture. This will provide the best protection for your CTD and will give you a -34 freeze protection. Cummins recomends changing coolant every 24,000 miles - they also sell a 50/50 pre mix.
1993 4X2 - 14 WG, PDR HX35, ATS exh, 4" exh, DD3+Injectors, "Green HP" Air Filter - custom intake, 6 gauges, 15%+ pump DennyT Stage II 3200 GSK. Horton fan, NV4500 5 speed, BD E Brake, 45 gal. Aero aux fuel tank, SBC, Tworline intake 394/880 0n #2 - 440/889 W/M.