300E transmission Lube

[robi99]

I have searched the forum but not seen any deinitive answers on this subject.
Is it OK to run synthetic tranny lube in a 1989 300E??
I put Mobil One gear lube in my transmission the last time it was serviced and have been very happy. The car had about 50K miles when I did it but there was absolutely no leakage. It also shifts beautifully at -20 degrees. I have been feeling good about my decision until I talked with my local MB dealer who says he will make a couple of phone calls but doesn't think synthetic is a good idea in this car. He went so far as to say he thinks MB advises to NOT use synthetic in this car. What do you all think??