Even if an engine does not require supplemental coolant additives for cylinder wall cavitation pitting protection, the common supplemental coolant additives available will improve general metals corrosion protection. Nitrite as found in the old Nalcool product, Pencool additives, Fleetguard DCA2, Caterpillar coolant additive, Baldwin BTE, as well as Wix and Napa products....will improve the ferrous metals corrosion resistance even if the engine does not need that additive for pitting protection. The other supplemental coolant additive is sodium molybdate. It is a potent aluminum corrosion protection agent as well as being part of the most robust pitting protection available. More engines are being built with increasing amounts of aluminum content such as cylinder heads, water pumps, as well as thermostat housings and now radiators. Coolant additives composed of nitrite and molybdate are sold by Baldwin as BTA, Fleetguard as DCA4 as well as there are several coolants that use the combination of nitrite and molybdate as all or part of the ptting protdection and general metals protection. The most common (but not the only) are Fleetguard ES Compleat, Fleetguard Fleetcool EX, Caterpillar ELC OAT with nitrite and molybdate, Caterpillar Diesel Engine Antifreeze Coolant, Shell Fully Formulated Phosphate-Free, plus a few others whose names escape me at the moment. It has been mentioned that mixing nitrite only or nitrite/molybdate additives causes problems. That is not true. Most coolant manufacturers will state that mixing of their coolant with other brands will not cause harm. Adding one to the other only increases the values of the total additive package. Stories about mixing are completely untrue. The last topic to be addressed is the belief that only wet liner engines need SCA. The original Caterpillar V8 diesel truck engines, 1145, 1160 and the later 3208 were all parent bore designs. Parent bores use the cast-in cylinder design. Those engines require the use of SCA or coolants formulated with SCA to protect against pitting failures. The original International 6.9, later 7.3, the 7.3 Turbo (PowerStroke) and the last one from Int' the 6.0 PowerStroke (DT345) all are parent bore designs requiring and SCA per International Truck and Engine Company. Ford may not always have agreed! The Cummins 5.9L, ISB 5.9 and the latest ISB 6.7 as well as the Duramax diesel are examples of parent bore diesels that do not have the need for SCA. As I stated before, using coolant with SCA provide much better anti-corrosion properties than plain 'green' antifreeze. Not required but will not hurt either.
