I am grateful that I have not experienced the cold cutoff problem you describe. I do not know where you would begin to diagnose, but keep us posted to your progress.

In regards to fluids, I have been using Mobil1 since 1996 10W30 5W50 etc any Mobil1 that I can get at good price and season allows, now that Mobil1 0W40 is available I switched to it. (I bought it at Mobil1 0W40 from Advanced Auto Parts cheaper than WalMart). I have only changed the the ATF once at 120K mi, I put in Mobil1 syn ATF. I did not bother draining the converted since the ATF and filter were so clean. I am not impressed by redline products.

92 400E 170K mi