Fantastic! I really appreciate all the help. I will probably give it a shot, I have an extra clutch. Hopefully this really will solve the problem as it's a real pain in warmer temps. Just like you it works fine once you get moving and when the fan does actually engage.

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marcucci,

Here is the Toyota part number:

10,000 Cst = 08816-10001

10,000 Cst Toyota Oil

I really think this will solve your problem and the problem of others experiencing warm vent temps at idle.

P.S. I split the halves of the clutch and used a heat gun to drain the old fluid out. Then I added roughly the same amount of fluid - eye balled the amount in the clutch before I drained and compared the amount removed and added using two identical cups.