I use mobil 1 . Stable to 1600F and aluminum melts at 1250 to 1300 so I know it will never be an issue.
We, I ran a 4150lb race car for many years with a 5100 stall converter and a transbraked torqueflite. Every few weeks I had to pull the trans and fix the inner sealing ring of the high clutch to stator support . I had already went to stainless but the seals would begin to fail and it would show up in my MPH by a unexplainable sudden loss in MPH. Got so I knew what to watch for and just dealt with it. One day a local oil dealer brought Mobil Engineer the late Mike Priest here. It was obvious he was drag car savy. He asked if I had high clutch troubles and I explained the above. He asked why I didn't use Mobil1 synthetic . I poo pooed it but he issued me the challenge quoating the figures I mentioned above. Back then it was about an $80 touch to use it. I swallowed hard and gave it a try. Five years later I was on the same trans as it had not had to be serviced since. In spring checkover even the kickdown band did not require adjustment. Eventually I broke a rear spraque and had to remove the trans and replace the sheared case however even though I checked them all none of the clutches or bands needed replacement. I since decided that that trans probably took more abuse then any other I will own however I still use synthetic at least in all my race trans. The doorslammer car used to run 1.52 60 footers at 4150 lbs race weight carrying the wheels sometimes a foot in the air. My pal Gary also uses it in his BB Mopar RED which we adapted a heavily reworked 904 trans to. I don't think it would survive otherwise. His car is an old Woody G touring car which was built to survive and has. Not particularly light for RED.
For me it was the cheapest $80 I ever spent.
don
