I would like to change the oil of my manual gear for 67 230SL. I am looking for the right oil and viscosity to use. The current manual transmission seems to have the original oil which has the regular oil color. As I read in the Forum, some posting suggest that the manual transmission oil should be replaced with ATF (red) oil. From my past experience, manual gear box usually use 85 Wt. oil. However, this kind of oil becomes very viscous in the cold climate of NY. I would appreciate any suggestions.