I just bought a 1997 Legacy Outback with a manual transmission. 248,000 miles and the synchro's in 1st and 2nd gear don't work fully and the car grinds when downshifting if I don't double clutch. I am taking it in to fully service it front to back and want to know what the absolute best fluid to use in this transmission would be.  I have read many posts here and seen several kinds recommended... many that actually improve things.  That would be great... if possible.  Also, how many quarts does the tranny/transfer case hold?  

 

Two brands mentioned here are the Red Line and the Royal Purple, both synthetic. Are these the best way to go? Either better than the other? 

 

If the fluid that comes out is really dirty, then I have learned here that I should plan on changing the fluid every thousand miles until it cleans up.  Is there a particular type I should use for this that will aid the process?  

 

I am a big fan of using the best fluids possible and have a 96 Mercedes C Class that has been running Mobil 1 since it was new and my new Subaru will get to enjoy it's final years with a similar quality oil.  Which reminds me, which viscosity synthetic oil should I run in the crankcase? 

 

Thanks for any advice you can give as I work to bring this aging soldier back to health. 

Edited September 13, 201312 yr by revtim

There's a huge thread at NASIOC dealing with "Scotty's cocktail" to help with synchro problems. It won't repair a car, but may reduce some of the clashing.

 

Most people say stay away from synthetic, but Redline Shockproof may be an exception due to the odd formulation.

 

I'd say, just try some fresh, name-brand but not expensive, NON-synthetic GL-5. If that doesn't help, maybe investigate the cocktail?

Edited September 13, 201312 yr by 1 Lucky Texan

The normal oil is just 80-90 GL5 gear oil. I would just try new oil before going crazy with synthetics and all that.

 

Engine oil you might be better off to stick with conventional or a synthetic blend. That engine has the small rod bearings that don't do well with thin oils. I'd go with 10w40 in the warm months, and switch to 5w-30 for winter.

I was looking at the Mobil 1 High Mileage oil for the crankcase but notice it's a 5X20W.  That surprised me. Is that too thin for the Subaru 2.5 engine with 250k miles on it?

If you live in Antarctica you might be able to get away with 5w20. But that stuff is way too thin for that 2.5.