The OATS that I'm familiar with in Dexcool and similar coolants are carboxylate, sebacate, and 2eha. Dexcool is commonly said to use 2eha and/or sebacate- depending on manufacturer. I've also read that some import coolants (Honda in particular- probably others) use sebacate, but not 2eha. All heavy-duty ELC NOAT coolants (including Texaco ELC) that I'm aware of list carboxylate as their OAT inhibitor.
Conventional wisdom around here is that 2eha is primarily responsible for Dexcool's much-discussed gasket incompatibilities. Whereas other (import) OAT coolants primarily relying on sebacate have no such reputation. If one could determine with certainty that a particular manufacturer of Dexcool used only sebacate- then IMO, this would be preferable for obvious reasons.
An issue that came up earlier in this thread is whether Texaco ELC uses 2eha or carboxylate. The links from Cummins Engine Company indicate that Texaco ELC uses 2eha- leading to gasket problems. Whereas Texaco's own literature claims that their product uses carboxylate (as do all similar ELC's). This leaves only two possible scenarios as far as I can tell:
1. Texaco ELC initially used 2eha, then switched to carboxylate once the gasket incompatibilities became apparent
or
2. Carboxylate is a more general term that encompasses several compounds, including 2eha.
My chemistry education is limited on one semester of college-level chemistry, taken several years ago... along with a year of chemistry in high school (well over a decade ago). So if someone with a better background in organic chemistry could confirm or correct my conclusions, it would be appreciated. But I've found several links indicating that the latter option (2.) is the case:
http://www.scribd.com/doc/1621299/Environmental-Protection-Agency-c14172rt9
http://www.wipo.int/pctdb/en/wo.jsp?wo=1998039283&IA=WO1998039283&DISPLAY=DESC
http://answers.google.com/answers/threadview/id/591732.html
http://en.wikipedia.org/wiki/Hexanoic_acid
http://en.wikipedia.org/wiki/Carboxylic_acid
All of the prededing links (none of which are
directly coolant-related) either explicitly state or imply that 2eha and similar compounds are carboxylates. Also, according to this link (
http://en.wikipedia.org/wiki/Sebacic_acid), sebacic acid (the 'other' OAT used in dexcool) is also known as 1,8-octanedicarboxylic acid.
From all this, I will conclude that any coolant that lists "carboxylate" as the corrosion inhibitor may be using 2eha, sebacate, or any of several other related organic acids. In other words, carboxylate=OAT... and is no more specific than that.