I’m starting to think 2-EHA might not be the bogeyman it’s thought to be. I’m using Prestone Cor-Guard in an older Sienna using the 3MZ-FE 3.3L V6. The thermostat housing/valley plates on the leak. It’s been almost 4 years since I did the repair - used Toyota’s expensive ThreeBond 1282B that’s supposed to resist coolant better - it was redone once with black RTV(either Permatex black or ThreeBond 1207B/Toyota 102) by Hertz or a dealer tech before my parents bought it as a CPO in 2006. The plate is still dry - it’s also a common issue with the newer UR-series V8s. I resealed a timing cover using Permatex Right Stuff 90-minute gray and that car uses Peak 10X.
While silicone and 2-EHA doesn’t play nice and both Prestone/OWI’s HD “premium” coolants with dual Cummins/Detroit approvals(Prestone Command Cor-Guard and Final Charge Pro-Series) don’t use 2-EHA, Permatex claims their “newest” Optimum series(and I assume Right Stuff) is Dex-Cool resistant and Toyota calls out 1282B to seal cooling passages. There might be some truth but also if the sealant is formulated to resist 2-EHA and other organic acids, it might be a moot point.