What is preferred? Synthetic or conventional transmission gear oil?

 

yea i was wondering the same. I am around the point where i need to change my tranny fluid and am undecided with what to go with. Some say only use oem fluid and others say going to a 75w90 syn makes a huge improvement.....

 

I think I am going to use Lubro Moly 75-90 Voll Synthese

 

I think I am going to use Lubro Moly 75-90 Voll Synthese

 

I think the consensus is that you need to use a GL-5-rated tranny fluid.

People have gotten grinding synchros from using Redline, etc. synthetic fluids, as they are GL-4 rated.

Some have had luck with the GM/Pennsoil Syncromesh fluid, either used solely or mixed with other fluids.

If you're hell bent on using synthetic, get some NEO sythetic fluid, its what the WRC team uses.

Otherwise, stick with the stock fluid...

 

no doubt the 5-speed is different, but i have not had luck in my STi using synthetic...so far I've tried redline 75w90ns and royal purple 75w90. my synchros don't like it. think i'm going to switch back to stock dino fluids soon...

 

The LM 75-90 is GL5 rated

 

nice!

you read any feedback on its use in BMWs and other cars?

 

Not yet. A lot of my customers are happy with it though.

 

I've tried Royal Purple, Redline and generic GL5 fluid from Kragen...

best one was the ones from Kragen, they work the best when the tranny is still cold.

Stock Subarus are filled with Pennzoil GL5 last time I checked with the subaru tech. I would just stick with that and save your money.

Tommy

 

I posted this question up a while back. I got a split answer. 1/2 one way and the other 1/2 another. I heard switching to synthetic from people on this board can cause grinding and when they switched back, it was fine. Others say that it makes the shifts much smoother and they haven't had a problem. I say try it and see what happens. It can't hurt. The only thing I can say is be careful with warranty. If you still have warranty, then call up a dealership and talk with them about it first.