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Both conventional and extended life antifreeze/coolant formulations use Ethylene Glycol for boil over and freeze protection. The difference is in the inhibitor packages mixed with the ethylene glycol. Conventional type antifreeze/coolant inhibitors do not last as long as extended life antifreeze/coolant inhibitors. Therefore, you do not need to add inhibitor packages (SCA's or Extenders) as often to extended life antifreeze/coolant.
SCA is the acronym for Supplemental Coolant Additive. These are additive packages, either dry or liquid, which are added to extend the useful life of the inhibitor package to protect the cooling system against cavitation erosion corrosion, formation of scale, cooling system deposit, rust and other unwanted cooling system degradation products generated as a result of the engine operation.
A “Type 2” supplemental coolant additive is based on Borate/Nitrite chemistry, while “Type 4” additives are based on Phosphate/Nitrite/Molybdate chemistry. They are two different technologies, and, for optimal performance, should not be mixed but they are compatible. See the engine manufacturer's recommendation for which type of SCA that should be used.
Heavy-duty extended life antifreeze/coolant utilizes an Extender. An Extender is an inhibitor package specially formulated for HD extended life antifreeze/coolant.
Both SCA and Extender’s are used to supplement engine coolants to provide a fully formulated heavy duty (HD) coolant. However, SCA’s and Extenders are as different as conventional low silicate HD coolant is to Extended Life HD coolants. SCA chemistry is typically based on a combination of nitrite and inorganic corrosion inhibitors, while Extenders are typically based on nitrite and organic corrosion inhibitors. The use of SCA’s in Extended Life coolants or Extenders in silicated formulations could limit the benefits of the additive.
Manufacturers do not recommend mixing heavy-duty conventional and extended life coolants. The resulting mixture would not be considered to be an extended life formulation, since conventional inhibitors would be introduced into the system.
If a heavy-duty extended life antifreeze/coolant is mixed with more than 10% heavy-duty conventional antifreeze/coolant the cooling system should then be maintained as a conventional coolant formulation.
Inhibitor levels in extended life coolants need to be maintained, the difference between HD conventional and HD Extended Life antifreeze/coolants are the service intervals between the required maintenance will be longer. Follow the recommended OEM service interval for the addition of extenders. Remember, it is important the correct fill levels in the cooling system be maintained. Any needed replenishment due to leaks or engine servicing must be made up with the correct mix of HD Extended Life antifreeze/coolant and water.
With the proper servicing and maintenance both heavy-duty conventional and extended life antifreeze/coolant could conceivably be used to the same end point. Extended life antifreeze/coolants require less frequent addition of an inhibitor package known as an “Extender.” Cooling systems using either formulation require coolant filter changes at the manufacturers recommended intervals. Routine testing on heavy-duty conventional antifreeze/coolants insures the appropriate additive levels, through the addition of supplemental SCA’s, as well as the use of the correct mixture of water and coolant. Coolant filters with the addition of SCA's should not be used with Heavy-duty Extended Life antifreeze/coolants. Use only coolant filters with NO SCA charge with Heavy-duty Extended Life antifreeze/coolants.
As long as the OEM recommended cooling system fill level, water to heavy-duty conventional antifreeze/coolant ratio and SCA levels are maintained and there are no catastrophic failures or system contamination, both heavy-duty conventional and extended life coolant formulations could be used for about the same amount of time.
Whenever there has been a repair made to the engine, which involved full or portion removal of the coolant, contaminants entering the cooling system, (defective oil cooler, head gasket, etc.) or with the catastrophic failure of a cooling system component, the system should be flushed before refilling with fresh coolant. Also, coolant that appears contaminated (rust, scale, etc.) or cannot be brought back within specification through the addition of SCA’s or supplemental new coolant should be replaced and the cooling system flushed. In any event, whenever a vehicle is being serviced coolant fill levels, freeze protection and SCA levels should be determined using a test kit or laboratory analysis. The appropriate measures should be taken to bring the SCA levels back within OEM specifications. When any formulation of coolant, conventional or extended life, cannot be brought back within the OEM specification or is contaminated it should be discarded according to local laws and regulations.
Recycling coolant or purchasing recycled products for use in your vehicles opens your maintenance practices up to additional variability in cooling system protection. Recyclers and re-cycling practices can vary dramatically from location to location. Some recyclers do little more than filter the coolant while others remove all of the inhibitors, corrosion products and other contaminants from the glycol and refortify it with a new inhibitor blend. The quality of the final recycled coolant is very dependent on the recycler. It is very important that you have an understanding of the technology the recycler is using to purify the glycol solution and the inhibitor technology they are using to restore the glycol back to a useful product (conventional, extended life, hybrid, etc.)
There may be no savings when comparing a highly refined recycled product to new coolant. The more closely the recycled product resembles “virgin” product, the more costly the coolant will be to purchase.
Additionally, since your coolant may be mixed with that from another fleet during the recycling process, there could be cross contamination by the addition of impurities to the product you receive back. For additional information about approve list of recyclers refer to TMC/ATA publication.
Antifreeze/Coolant color, as a result of TMC efforts should directly correlate to the type of coolant and its’ formulation. However, care should be taken since not all antifreeze manufacturers may be following the recommended TMC guidelines. Prestone's Heavy-duty antifreeze/coolants follow TMC recommendation on antifreeze/coolant color identification for both Conventional and HD Extended Life coolant formulations.
The important things to remember about coolants and your engines’ cooling system protection are:
- Follow the OEM recommendations regarding cooling system maintenance practices, service intervals, type of coolant formulation and correct concentrations with water. Record and follow service recommendations for the specific formulation used in the vehicle being serviced.
- Change the coolant filter as recommended by the OEM.
- Do not mix coolants of different formulations unless absolutely necessary. Refer to engine manufacturer recommendation before mixing different coolant technologies If you don’t know what formulation is in a particular cooling system find out (through laboratory testing) before taking a guess and mixing formulations.
- Test the cooling system at regular intervals to determine the concentrations of additives and freeze protection. Replenish additives only to a level as recommended by the OEM, more is not necessarily better. Use SCA’s or an Extender manufactured specifically for the formulation of the coolant in the vehicle (don’t use an extended life SCA with a standard formulation).
- Maintain coolant levels within the system, with a make-up mixture of known mix and additive concentration. Check for leaks, and repair the system as required. This will prevent the use of make-up coolant from unknown and unreliable sources while in service, which could upset the balance of supplemental additives and freeze protection or contaminate the system.
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