Phosphates in Conventional Heavy Duty Coolant: Good or Bad?

[viscous]

Conventional heavy duty engine coolant is typically one of the following:
1. Low-silicate conventional green automotive coolant meeting ASTM D4985, plus an appropriate dose of SCA
2. Fully-formulated (pre-charged) heavy duty engine coolant meeting ASTM D6210
The first option typically contains phosphates via the conventional automotive coolant. The second option, however, is usually phosphate-free (e.g. OWI Fleet Charge). What is the result of choosing the option that contains phosphates, rather than the one that doesn't?

 

[Donald]

I am not sure of the chemistry. Not a chemist. But for me I would either buy OEM coolant or a coolant that meets the manufacturer's specs. I assume you are talking about a diesel engine which is typically an expensive engine.

 

[MolaKule]

Engine Coolant Basics

Coolant (or antifreeze) protects your engine from freezing while defending components against corrosion, as well as plays a critical role in sustaining overall engine heat balance by removin…

www.machinerylubrication.com

 

[wpod]

coolant chemistry is changing as fast as the seasons seem to be changing.

 

[JohnnyG]

The article linked above does a good job of describing the intricacies of coolant, a very complicated subject to be sure.
It does mention freeze protection as one of it's basic functions, but skips over Boilover protection early on, though it is touched on later in the article. I have also been assured that the new OAT technology was developed prior to all aluminum block engines in a different thread, but found this paragraph yo be interesting to say the least:

The implications of this functional difference are enormous: extended life cycles, unsurpassed hightemperature aluminum protection, as well as heat transfer advantages on both hot engine surfaces and heat-rejecting radiator tubes where heat transfer is critical to optimal performance. Highquality carboxylate-based coolants have demonstrated performance of more than 32,000 hours in stationary engine applications without being changed.

Aluminum blocks or even just aluminum heads on iron blocks are subject to uneven thermal expansion, so good temperature control is critical.

So it is important to stick with the type of antifreeze recommended by the manufacturer. Also to surmise what I've been told by a GM engineer, switching to a silicate based antifreeze in an engine not designed for it requires coolant changes every 2 years! No more long life, 5 year/50,000 mile changes. It is also not reversible, once you put in silicates, they never go away. He also said that silicate containing antifreeze in an engine not designed for it will likely wear out the water pump seals much more quickly.
And finally, watch the concentration and the PH of the coolant, good tips!

 

[viscous]

Engine Coolant Basics

Coolant (or antifreeze) protects your engine from freezing while defending components against corrosion, as well as plays a critical role in sustaining overall engine heat balance by removin…

www.machinerylubrication.com

According to Fritz, sounds like phosphates are fine if the coolant concentrate is not mixed with hard water. In other words, option 2 has no advantage over option 1 when using distilled water. Would you concur?

 

[nthach]

I think Isuzu calls for a Japanese pHOAT coolant in their diesel cab overs, but Dex-Cool for the gassers. Hino uses pink or blue pHOAT - same as Toyota or Subaru. The HD engine makers seem ambivalent about phosphate, the trend there is a NOAT coolant using nitrite for the wet sleeve liners.

Prestone just introduced a HD version of Cor-Guard, but this formula is 2-EHA free - like a Japanese coolant.