I just changed the gear oil in my '06 6MT Sedan using Mobil 1 Delvac Syn Gear 75w-90 ( ). I was trying to re-order the standard Mobil1 75w-90 synthetic I used last time, but it was either overpriced or out of stock. After some searching I found the Delvac, which was slightly more expensive than the standard synthetic, but not by much. I read some (probably bogus) threads about how a couple Porsche cup teams (it's always Porsche cup teams) prefer it over Porsche factory fluid yada yada yada, so I figured I'd give it a try, and since I'm happy with the results, I thought I'd share the info!

I ran the recommended Nissan 75w-90 fluid in a previous G with the C009, which was fine but overpriced. I soon found myself in this G, and not knowing the history of the car I immediately refilled the transmission with Mobil 1 75w-90 synthetic, which I ran for 30k miles until this fluid change. After buttoning everything up it was immediately apparent that this 'Delvac' fluid provided smoother shifts than I had ever experienced in a G. It's still a little notchy in cold weather (~35°F), but even then I don't feel the need to double clutch as I did with the standard 75w-90, and once it's up to temp the shifts are as buttery smooth as they have ever been, if not more butterery . I've only been running this fluid for 75ish miles so we'll see how it holds up, but my initial impression is very positive.

Be warned though, the container I linked above is only 4 quarts, which is plenty for the transmission, but if you're planning on doing the diff too, you'll need at least one more quart (two more to be safe). I ended up mixing the remaining Delvac with 1 quart of the standard 75w-90 synthetic for my diff, which worked out fine.

 

I stick with the oem tranny fluid.

If you are having to “double clutch”, I would suggest that none of your choices in fluid are good nor worthy of recommendation to the forum.

 

My original choice in gear oil is also your preferred gear oil, so how about I climb up on this big, huge, massive, giant high horse so you can hear me when I suggest that none of your choices in fluid are good nor worth of recommendation to the forum.

Joking aside, maybe I'm just a sh*tty driver, but I had to double clutch in cold conditions with the OE fluid too. Either way, if you want to spend $20/quart on the OE stuff, it's no skin off my back.

 

You probably don't actually have to release the.clutch to get it to go in, usually if you just wait for rpms to fall you'll find a sweet spot when the input/output speeds are the same and it falls into the next gear, just keep light pressure on the stick.

 

Having to double clutch generally means one does not know how to properly drive a manual shift.

Telcoman

 

Badly worn synchros and frigid temperatures together can make for an frustrating shifting experience for MT folks. It's still a matter of getting the nose cone to bring the gear up to the same rpm but poorly flowing lubricant plays a huge factor. On a new transmission you''re still going to notice a "sluggish feel" trying to bang from one gear to the next QUICKLY on a cold tranny. With a worn nose cone on the synchro it just takes MORE TIME to bring the gears to the same rpm rpm so they can mesh.

The issue should fully disappear once you've driven about 1 mile in freezing temperatures though.

 

I’m just saying, sounds like you’ve got bigger problems than tranny fluid.

 

This thread has kinda derailed - to clarify, I was not double clutching out of necessity to avoid grinding gears, I was doing it to expedite 1 - 2 changes in cold conditions until the transmission was up to temp. I only mentioned double clutching to illustrate that in my experience the OE and regular M1 75w-90 fluids were both notch-y in cold conditions to the point that double clutching made it easier to change gear. With the new fluid, double clutching doesn't make a difference.

Also, I felt like a cool guy saying 'double clutch'.

Heel toe, Scandi flick, left-foot-trail brake, double clutch.

Try it, you'll like it.

 

If you're having issues with 75w-90 try running 75w-85 since they've both listed in the FSM.

Also of note, the transmission and differential don't use the same fluid, rear diff is 80w-90.

 

I have a JWT clutch and flywheel and during one service my mechanic at Nissan put in some other tranny fluid that he said they put into all the manual Zs and it did not work well at all with my JWT. I’m betting it was probably the 80w 90 cleric mentions above because it was a bulk fluid. Went back to oem fluid and it was perfect again.

My mechanic is their lead technician and their GTR mechanic whom I’ve known for a long time, so I trust that he was telling me he truth that they used this alternative fluid for their Zs. So, perhaps the JWT is more sensitive, and at that the oem fluid worked perfectly, thus why I’ve not strayed from the oem fluid.