I inquired about their D6 ATF. I was curious if it's compatible with Hyundai SP-IV-RR and Dexron HP. I also inquired if they use Group III base oil in their ATF or High Performance motor oils. I found his reply about the D6 ATF a little bit strange because Hyundai SP-IV-RR came out after Dexron HP, and it's more than likely based on it. I could be wrong. I believe they're not confident that GM transmissions calling for Dexron HP will not shudder using RedLine D6. It's silly and it's more than likely a lack of testing on RedLine's part. As
@MolaKule stated previously, the shudder issue was cause due to the original black label Dexron HP fluid (Afton add-pack) being hygroscopic. At least his reply was honest, and I sure appreciate that. Especially since AMSOIL ATL uses the same DI package as RedLine D6, yet AMSOIL claims Dexron HP compatibility. More than likely AMSOIL did more testing to ensure that compatibility.
As for not using Group III base oils, I believe that as well. Here is the reply from Red Line:
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