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Part I: Choosing and Using a Supplemental Coolant Additive
by Ed Eaton, Amalgatech
Appeared May/June 2000 Cool Profit$ Magazine
© 2000

Other Parts:
Table 1: Antifreeze / Coolant Glossary
¤ Part II: SCA Tech Talk
¤ Table 2: Pencool to Fleetguard Comparison
¤ Table 3: Recommended SCA Usage By Vehicle Manufacturer
was at a GM car dealer the other day looking for a used truck for my daughter. We were test-driving a 1995 model, one of the last model years that GM used conventional "green" coolant. I made a remark to that effect to the salesman, and learned that this fellow had no idea that GM cars and trucks have had DEXCOOL® orange-color coolant in them since 1996 or 1997, depending on the model. Obviously, there was no use asking him if he knew that this truck, according to GM, needed an SCA (Supplemental Coolant Additive). The reality check of the salesman’s ignorance was just the nudge I needed to start writing this article. Since I’m up to my neck in coolant problems and chemistry every day, I easily forget that outside my little coolant laboratory very few people know anything about antifreeze. And frankly, my dear, they don’t give a darn! Well, at least not until they end up in your shop whining about the repair bill!

Three main types of antifreeze.
Before getting too deep into SCAs, let’s review the simplest definition of antifreeze: ethylene glycol or propylene glycol blended with a package of corrosion prevention chemicals. When mixed with water, usually at 50%, it becomes coolant. There are many types of antifreeze, but three are most important:

  • Automotive antifreeze (for cars, not intended to be maintained with SCAs). These are characterized by ASTM specification D-3306.

  • Low-silicate heavy-duty antifreeze to which SCAs must be added before use. These are characterized by ASTM specification D-4985 ("Standard Specification for Low-Silicate Heavy Duty Antifreeze Requiring an Initial Charge of Supplemental Coolant Additive"). They are becoming obsolete.

  • Fully formulated heavy-duty antifreeze that already contains the SCA components. These are characterized by ASTM specification D-6210

Mainly only two types of SCAs.
SCAs have been providing corrosion protection to cooling system components for a long time, and are used worldwide. Several companies manufacture and/or market quality products, but there are clearly two leaders who pioneered SCA chemistry. Because most of the others try to "follow the leader," I will focus on these two primary technologies and their differences. The ASTM Standard Specification for Fully Formulated Engine Coolants refers to the two approaches as "Type A," exemplified by Pencool®, and "Type B," exemplified by Fleetguard DCA-4®. For cooling system technicians, they represent the vast majority of the market, they are ASTM compliant (D-5752 "Standard Specification for Supplemental Coolant Additives (SCAs) for Use in Pre-charging Coolants for Heavy-Duty Engines"), and, you can’t really go wrong using them—if you follow the directions.

Why SCAs exist.
At first there existed just the top two of the ASTM specifications listed above: 1) ASTM D-3306, and 2) ASTM D-4985; ASTM D-6210 was added recently. It establishes the new standard for heavy-duty antifreeze that includes the cavitation protection as provided by SCAs. This product is ready-to-use (after mixing with water) right from the jug or drum.

D-3306 calls out the physical and performance requirements that new (non-recycled) automotive antifreeze should meet. Don’t buy product that fails to at least claim it meets this specification. This type of antifreeze usually includes a pretty stiff dose of silicate to protect aluminum for two or three years.

Because operators of Heavy-Duty diesel engines experienced problems when using the car antifreeze, a "low silicate" specification was developed. These antifreezes contain less silicate and are designed to be maintained (tested and, if necessary fortified) on a periodic basis. Importantly, as indicated in the title of D-4985’s specification, this antifreeze isn’t "ready-to-use;" an SCA must be added!

Proper use of an SCA.
For cars and many gasoline powered light trucks (pickups):

  • Type 1: Mix half antifreeze and half water. Automotive (D-3306) or Fully formulated (ASTM D-6210) antifreeze may be used. Prepare the coolant by mixing the antifreeze and water and then filling the coolant system. SCAs are not usually used in these vehicles.

For all diesel trucks and certain gasoline powered trucks (2 tons and up, as well as specific trucks identified by manufacturers):

  • Type 2: Fully formulated antifreeze is strongly preferred (ASTM D-6210 specification). Examples include FleetCharge®, Fleetguard Compleat®, Houghton’s MacGuard 2792®, Prestone® Heavy Duty, Quaker State, and all of the engine companies’ brands (Cat, Cummins, Detroit Diesel Corp., Mack). Mix the antifreeze with water at 50% each. Then maintain with SCAs as recommended by the engine manufacturer (general guidelines follow).

  • Type 3: D-4985 "low silicate" antifreeze must be mixed with water, usually at 50%, and then the SCA is added, usually at 3% (1 pint to 4 gallons). The SCA can also be added by using an appropriate "pre-charge" coolant filter. When the water, antifreeze and SCA are mixed and put into the system, the coolant is capable of protecting the diesel’s cooling system. SCAs exist because conventional antifreeze for heavy-duty use was incomplete, and SCAs had to be used, without exceptions, in every heavy-duty engine.

SCAs have been used in gasoline-powered vehicles with success to solve specific vehicle problems. GM charged every light and medium duty truck that left the Janesville, Wisconsin truck plant, gas or diesel, with Nalcool® 2000 brand (now renamed Pencool® 2000) SCA for years. The use of Nalcool for routine maintenance is still specified by GM technical bulletins for many trucks, including the model in the last Cool Profit$ article, "Why good radiators go bad quickly." I don’t want to leave Ford out; they use and recommend maintenance of diesel-powered pickups with Fleetguard DCA-4® brand SCA.

Coolant that contains no antifreeze.
Both Penray and Fleetguard have spent buckets of money to research, develop and independently certify their SCA technologies. These products are so good that in fact, they are often used to treat plain-water cooling system for vehicles operating in warm climates. Using plain water is very controversial, it isn’t recommended by any OEM. Nevertheless, the railroads and many mines use treated water in large diesel systems. The practice is also seen at many transit bus companies in warm climates.

Additional usage of SCAs.
Besides heavy-duty diesel systems like those used in highway trucks, mining equipment, stand-by power generator sets, marine engines, etc., most light duty diesels also benefit from an SCA as well. Note that there are the two stages in the correct use of an SCA:

  • Stage 1: Initial Pre-charge. Use 50% fully-formulated antifreeze and 50% water, or, Mix 50% water and low-silicate antifreeze (ASTM D-4985 specification). Add 3% by volume (1 pint to 4 gallons) SCA. If you’re one of those mavericks using water without antifreeze, mix 5% SCA in water (1 pint to 10 quarts).

  • Stage 2: Maintenance. Every 3 to six months, test the coolant for freeze point protection using a coolant test strip. Be sure to use the strip supplied by the SCA manufacturer. The two technologies are different, and using the wrong test strip will eventually cause you headaches.

If the freeze point protection is acceptable, continue on to the next step. If not, correct the freeze point. Adding pure antifreeze to the coolant will lower the freeze point. It’s also common to find that the antifreeze is too concentrated, requiring that it be diluted with water.

Check the SCA concentration reading on the test strip. Add SCA (by filter or liquid) only when the level is low. Don’t worry, there is plenty of safety margin built into the products. Don’t overdose the system; overdosing sometimes creates a really nasty mess in the radiator.

Important: DON’T use SCAs in DEXCOOL coolant unless you know exactly why you’re doing it. This does require the advise of a coolant specialist.

Supplemental Coolant Additives (SCAs) are great weapons in the war against premature cooling system failure. They are absolutely necessary in, and required by manufacturers of, heavy diesel engines and some light diesels. Anything bigger than a car is a candidate. You use 1 pint to 4 gallons to start a system, and then "as needed" based on testing after that. A new kind of antifreeze called "fully formulated" antifreeze does not require a pre-charge of SCA because it is already built-in. Test the coolant every 3 to 6 months. Systems that leak a lot or run around the clock may need closer supervision. Ask a QUALIFIED technician at the engine OEM service department for specific recommendations for your equipment. If he doesn’t sound like he knows what he’s talking about, get the OEM’s coolant guide. They all have one! $$$

Product Information:
Fleetguard: www.fleetguard.com/products/pcoolant.html;
Pencool: www.penray.com/HD
CPM: For those seeking advanced training in Coolant Technology, continue with Part II, "SCAs Tech Talk."

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