I use Water Wetter in my old C10 V8 with dual electrical cooling fans. I like it.

What is your fan configuration?

Can you add a mechanical fan? Does a V8 electric fan fit an I6 3.0 auxiliary fan connection?

I would try the less coolant and more water percentage. Or more air flow. Are all the fan assembly fins in place?

Are the fans brushless?

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'06 X5 3.0i - bought @143,123 miles (12/26/20)