I have a Japanese made '90 Corolla LE with 4A-FE/5 spd manual. How do I find out if it's a C50 or C52 transmission? I called the local Toyota dealership parts department and they could not tell me after running my VIN. The transaxle lubricant called for is 75-90w gear lube. Can I use Mobile1 80-90w synthetic gear lube without causing any problems? Would there be any cost effective results in doing so, or should I just stick with the manufacturer's recommendation? Thank you for your time and consideration. Rob