After all the recommendations and the additional research on the internet I have decided to use 70w gear lube. Which has the same viscosity of 5-30 motor oil but will not break down as quickly as motor oil. ATF is thin, works well at low temps, and is good for a slight decrease in drag [better economy]. But I think the 70w gear oil would be better for shifting and wear.
Thank you all for your advise.
