Ford's strategy to tap its global engineering resources for new vehicles at lower cost relies on standardized production processes and reduced complexity. One subject area that is getting attention is the company's choice of antifreeze coolant.
Although antifreeze is 93-95% ethylene glycol and is mixed 50-50 with water for use, the corrosion inhibitor package is specific. Ford uses three different ethylene glycol-based coolants in its cooling systems, each with a totally different corrosion protection chemistry, which if mixed in service, would weaken the one chosen for the factory fill.
Further, sourcing and distributing three different formulas—with two different ones specified for the same engines in a number of cases (depending on the production line)—raise both logistical and cost issues.
So Ford has begun a world-wide conversion to a single coolant, but that's not just a matter of a simple purchasing decision. The different coolant formulas are in place for technical reasons, and completing a changeover is a multiyear project that in some cases will wait for complete phase-out of engines.
Ford Europe's influence
Although antifreeze dye colors have no technical meaning, they do assist in identification. At Ford, there are three extended-life coolant formulas in current use. As an indication of how influential Ford Europe was in the decision-making process, the choice for worldwide use is an orange-red dye OAT (organic acid technology) formula, which has been the Ford-Europe production line coolant.
An OAT formula has no silicates or phosphates, two of the traditional inorganic inhibitors used to protect the cooling passages of the engine and the water pump chamber. The Ford-Europe OAT formula contains sebacate and 2-ethyl hexanoate (2-EHA), a long-established combination of organic acids, plus a copper-brass inhibitor, typically tolytriazole or benzotriazole. It is similar to a "DexCool" formula GM has been using.
The other Ford formulas are deep green and yellow. Deep green is a phosphated "hybrid" organic acid technology (P-HOAT) antifreeze. Phosphates are particularly effective in quickly re-protecting the chamber of a water pump that has been pockmarked by imploding coolant bubbles from cavitation. The organic acid inhibitor that classifies it as a "hybrid" OAT is sebacate. And there is also tolytriazole for copper-brass protection.
Most Asian car coolants today contain a similar formula, although with other dye colors. Asian makers prefer phosphates to silicates, which display undesired effects in certain laboratory tests they use.
Mazda was involved in development of the Ford 3.5-L and 3.7-L V6s and 2.3-L and 2.5-L inline fours, variants of which Mazda also uses, so many of the applications are filled with deep green coolant, the Mazda OE choice.
Yellow is Ford's HOAT with silicates (S-HOAT) instead of phosphates. Silicates work the fastest to virtually "paint" the walls of the cooling system for protection, and they also re-protect water pump chambers pockmarked by cavitation. The silicates are in an inhibitor package with benzoate, the organic acid, plus nitrite to prevent diesel liner pitting, and benzotriazole for copper/brass protection.
Silicates are widely employed in Europe, where phosphates produce scale deposits in a severe hard water test the European makers use.
OAT for new gas and diesel V8s
Unlike silicates and phosphates, which deplete as they go to work coating the cooling system, OAT-alone formulas have very long service life. But OATs work very slowly, perhaps taking over 5000 miles to form a protective oxide surface. So they are unable to provide the fast re-protection of cavitation-pockmarked surfaces in water pumps.
If a cooling system is prone to cavitation and the vehicle is used in the kind of load service that is conducive to it, the pockmarking increases and can corrode, affecting water pump service life. As a result, Ford has continued with the yellow S-HOAT on the older 4.6-L and 5.4-L V8s and will not change, as these engines are planned for phase-out.
Ford' two new gasoline V8s, the 5.0-L used in the Mustang and the 6.2-L for F-series trucks, as well as the new 6.7-L diesel V8, have been designed to minimize water pump cavitation. So they are being filled with the OAT right from the start.
Ford said the cooling systems in its carryover V6 and I4 families also have been validated for the OAT (with cooling system modifications where necessary) and will get the OAT on a phase-in basis. The European-design models, of course, have been validated for the OAT from the beginning.
Diesels normally require specific protection against vibration-induced cylinder liner pitting, typically a dose of nitrite in the antifreeze (as in the S-HOAT). However, Ford said its new 6.7-L diesel was engineered for minimal piston slap and the OAT alone would provide adequate protection against pitting.
One of the organic acids, 2-EHA, is a plasticizer, softening some synthetic rubbers and plastics, particularly silicone gaskets and the Nylon 66 used for gasket carriers and radiator tanks. This was another reason for the continued use of the S-HOAT in the 4.6-L and 5.4-L V8s. All OAT-equipped engines have silicone-free gaskets and validated Nylon 66 radiator tanks.
Systems with OAT antifreeze are more sensitive to low coolant levels, because the OAT provides best protection when in full contact with coolant passages. The issue is acute with cast-iron engine architectures, but one also exists with aluminum. However, Ford has been attuned to the low coolant issue even with its S-HOAT, and its engines have a cylinder head temperature sensor and/or coolant level sensor.
For the OAT systems, the sensors combine with improved powertrain computer algorithms for detecting overheating and deploying the limited engine performance strategy Ford has been using to prevent damage to engines if coolant level drops significantly.
Additionally, Ford upgraded cooling system seals, gaskets, and clamps, and it evaluated (reworking where necessary) the assembly line processes to ensure a full fill. Further, the antifreeze is mixed 50-50 with de-ionized water for consistent new vehicle protection across all product lines.
The OAT carries a service recommendation for cars of six years/100,000 mi (161,000 km) for the factory fill, three years/50,000 mi (80,500 km) thereafter. The interval for diesels is six years/105,000 mi (169,000 km) for the factory fill in normal service, three years/45,000 mi (72,400 km) thereafter.