Engine-coolant compatibility is a puzzler

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This article was published 13/11/2009 (5874 days ago), so information in it may no longer be current.

QUESTION: I have a 1998 Explorer 4.0-L SOHC V6 engine with 84,500 kilometres and I want to change the coolant in the engine. I checked my owner’s manual and it states I should use Ford Extended Life Engine Coolant (DEX-COOL). I contacted a Ford dealership and asked if I could use the Prestone DEX-COOL Extended Life coolant. I was told the coolant required for my engine is DEX-COOL but he said I should use the Ford product as stated in my manual.

I also own a 2003 Cadillac 4.6-L engine with 88,100 kilometres. I want to do the coolant change in this vehicle next year using the Prestone DEX-COOL coolant. The Prestone DEX-COOL antifreeze/coolant information on the back of the container states it is compatible with other DEX-COOL-approved coolants and it also meets the Ford specifications for my Explorer. I am convinced the Prestone brand as mentioned above is safe to use in both of my vehicles. I will flush the engine using the Prestone Super Flush product and refill using the Prestone DEX-COOL Extended Life Antifreeze/Coolant.

On another note, while I was at PartSource, I discussed this matter with a behind-the-counter personnel who used to work repairing automobiles. He said I should flush my engine completely using a good flush/rinse product and make sure there are no traces of DEX-COOL left in my engine and then refill it with an ethylene glycol coolant. He states the glycol coolant is friendlier to the aluminum parts in contact with the antifreeze/coolant. Could you share your thoughts on this matter please?

ANSWER: Of course, a Ford garage would tell you to use Ford products. Both Ford and GM, as well as many other manufacturers such as Toyota, Honda and Mercedez-Benz use extended-life organic acid technology (OAT) coolants but the additives in the coolants for the different manufacturers do vary, and that is why the manufacturers want you to use their own specific coolant. Most Fords do not use DEX-COOL. However, there are antifreezes such as Prestone coolant that have been developed to meet the needs of many manufacturers and if it meets the Ford specifications, then it is suitable for use in your Explorer. As it also meets the GM specifications, it can be used in both your vehicles.

As for using a flushing product, I am hesitant to use one unless there is an indication of corrosion buildup, oil film in the coolant or heating problems with the engine. As an organic-based antifreeze, one of the ways extended-life antifreeze protects the various metals in the cooling system is to coat the parts with a very thin protective layer. Flushing chemicals in the system could remove some of this layer. I would only flush the system if I were switching to a conventional "green" ethylene glycol-based coolant. Rather than using a flushing chemical, drain the system and flush it with normal water. Then add the new coolant. Be sure to dispose of the old coolant in an environmentally friendly manner — it can be recycled.

Finally, there are many claims that DEX-COOL antifreeze has caused engine problems in GM vehicles, so some do recommend switching back to a regular antifreeze. I haven’t seen problems I could trace directly to DEX-COOL, and OAT coolants do protect aluminum parts. I would personally continue to use it.

QUESTION: I had nitrogen gas installed in my tires when I had them switched over to new winter tires. What happens if I fill them with air now that there is nitrogen in them?

ANSWER: Tires filled with nitrogen rather than ordinary air will maintain their pressure about three times longer. The oxygen molecule, about 21 per cent of air, is smaller, so it leaks out more easily. You should still check tire pressures regularly, however.

Advantages of nitrogen include slower leakage and no moisture. Moisture introduced into the tires will cause inflated pressures to increase much more as the tire heats. Race cars use nitrogen for this reason. Moisture can also corrode parts, and with the tire-pressure sensors now installed in many vehicles, this may help prolong the life of the sensors. Disadvantages of filling with nitrogen are the cost and availability.

If you top up the tire with normal air, you are losing most of the advantages of nitrogen, so you might as well have filled it with air initially. Availability is the big issue for most people.

Jim Kerr is an experienced mechanic, instructor and member of the Automobile Journalists’ Association of Canada.

kerr.jim@sasktel.net