From the Manual :

Manual Transmission

Selection of Lubricant

No fluid service is required. Use only fluid approved to
MB 236.2. SAE 5W-20 engine oil, meeting API SL or GF-3,
may be substituted. Refer to the Recommended Fluids,

Lubricants

 

While I was referring to putting it in the transmission, it is engine oil indeed

You are good with any approved or high end 5w20 that conforms to the standards Josh posted.

Probably worn enough to be 'smooth' I personally prefer the tightness mine has...

 

At about 87,000 original owner miles my 6 speed is running better than ever......I typically take it up to 2500 to 3500 RPMs on that 1-2 shift &........nothing but SWEET!

 

I know, I bought Mobil 1 5W20 for mine.

I thought what I was quoting made my meaning clear - but I guess not!

 

We've had this discussion over and over in the SRT4 world. We even had a Chrysler engineer that had a hand in designing the 5 speed tranny for the NSRT chime in and he told us that as long as it was a high-ZDDP oil that it would be fine. Mobil1 syn oils that met the criteria were only the "high mileage" oils, specifically 10-40. The only other consideration is the coefficient of friction (the NSRT required friction modifier) so if guys are running their MANUAL transmissions already with syn without grinding then I would say that it is fine. It will not ruin any internals.

That said, the word manual is capitalized because this does not apply to the auto trans for the Crossfire. (my CYA statement heh).