Part I: Choosing and Using a
Supplemental Coolant Additive
by Ed Eaton,
Appeared May/June 2000 Cool
1: Antifreeze / Coolant Glossary
¤ Part II: SCA Tech Talk
2: Pencool to Fleetguard Comparison
3: Recommended SCA Usage By Vehicle Manufacturer
I 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
Three main types of
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
(for cars, not intended to be maintained with SCAs). These are
characterized by ASTM specification D-3306.
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.
heavy-duty antifreeze that already contains the SCA components.
These are characterized by ASTM specification D-6210
Mainly only two types of
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
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):
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
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
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
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.
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
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 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
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! $$$
CPM: For those seeking
advanced training in Coolant Technology, continue with Part II, "SCAs Tech Talk."