Just missed a shift in my '88 GXL and the tranny is in the shop for a rebuild. I am being told by the rebuilder that I should be using 20/50 motor oil with additional additives rather than 75/90 Royal Purple and the tranny will last longer. He says that gear oil will ruin the tranny in short order and probably caused my shift problem. Am I crazy or is he? This car has 160,000 miles on it and has always had just ordinary gear oil in it. He's going to improve on that with motor oil??? What are your opinions?

 

I just switched over to royal purple in my tranny, and it has never been so smooth. This was only 160 miles ago, on a 160+k tranny, so... I don't really know what to say there...later

 

sounds like your tranny shop guy wants you to bring back the car for a tranny rebuild every couple of years, if he is telling you to put in 20W50 in a tranny that is designed for 90W

 

people have used the heavier gear oil in manual transmissions and rear ends for years and it has never been know to cause a problem. I think he's smoking crack.

 

Who do you trust more, Mazda or your trany guy?

 

Redline MT-90 is what you need

 

i second the redline mt-90... either that or royal purple... both have had nothing but great reveiws. I personally am running redline mt-90 in my tranny, smooth as buttah... and before i did this, i had a slight grind in 2nd too! all gone!

 

Thanks for all the input. Problem is all straightened out. The guy was talking transmission but was thinking engine. Just a bad day I guess plus he's the boss and, fortunately, is not the one rebuilding the transmission. Because of availability we're going back in with Royal Purple 75/90. In an area such as Lamar, CO. you quite often take what you can get, which isn't much. Thanks again!