Mobil 1 with XL-7 (new FM for use w/ synthetic) seems best for cold weather. I've heard many cold problems with Redline in here and SHOForum as well. Sounds like your tranny is having some issues if it is grinding with any fluid.

-'96 SE MTX 3L -'98 SVT 1,173 of 6,535 -'05 Mazda 6s, loaded, g/f's ride -Need a 96-00 manual on CD? PM or email me