Eneos 75w90 gear oil a godsend
 

I don't know if this is the appropriate sub-forum to post this, but given how wonderful my experience has been with this product (and how many headaches I had trying to diagnose my transmission issues) I just wanted to put this out there. I wish I had known about this sooner and hope it helps folks with similar problems!

When I purchased my 2007 6mt (1 year and 10k miles ago - car had 65k when I bought it and extensive dealer service records, well cared for), one of the first things I did was change the stock trans fluid to Red Line MT 90. The car had been shifting fine prior to the fluid change, I was just doing this as preventative maintenance based on the recommendations of many of you. Upon changing to Red Line, the car shifted SLIGHTLY harder and gear noise was SLIGHTLY more apparent. Nothing serious though. I'm talking very, very slight changes on both accounts.

Within the past couple of months, my transmission began to exhibit some worrisome symptoms. It didn't grind, per se, but shifting from first to second was often 'hard', as if there was some sort of mild synchro issue. Forgive my vague description, I just don't know exactly how to describe the sensation. It felt like a mild, split-second metal-on-metal resistance. Occasionally a mild metallic 'clunk'. Shifting into third through sixth was fine, but a bit more labored than usual. Shifts were accompanied by increased gear noise as well - albeit no actual grinding.

Needless to say, these symptoms had me worried as I did not want to replace my transmission. Knowing that my transmission fluid was quite fresh (and full, I checked the level), I looked for possible culprits. I noticed that my clutch master was leaking very slowly near the firewall. I replaced the clutch master and slave cylinders and bled the system to rule out the possibility of hydraulic system failure. This helped a bit, but not much. I also adjusted my clutch pedal, increasing total travel slightly. This helped a bit more, but I was still getting the occasional hard shift. In my estimation, these combined efforts improved my symptoms by 20% (in both frequency and severity of my hard-shifting symptoms).

As a final measure, I turned to my transmission fluid. This past weekend, at the recommendation of BHR, I swapped the 10k-mile-old red line for ENEOS 75w-90 gear oil. The car took almost exactly 2 quarts of the new fluid (I drained/filled with the car perfectly level using a bubble level). Old fluid was fairly dark and mucky, and the drain plug had a fair bit of metal shavings on it.

So far, I have around 75 miles on the ENEOS fluid and I am stunned at the difference it has made. I haven't had a single hard shift, and gear noise has all but vanished.

In hindsight, I am glad I replaced the clutch hydraulics because i did have a leaking master cylinder. But I'm not satisfied that the hydraulics were the problem. So for anyone experiencing my symptoms (or worse), I highly recommend ordering 2 quarts of ENEOS gear oil and swapping it in. It's $20 a quart on amazon so $40 for the 2 quarts you'll need. It made a world of a difference for my transmission.

For reference, I test drove an R3 with 20k miles about a month ago and my car now shifts just as easily/smoothly.

And i'm not bashing Red Line at all - I know many here have had great luck with it. I have no idea why I did not have such luck.

If anything changes or things get worse again, I will update this thread.

[SIZE=3]NOTE: For my detailed how-to with pictures, go to my DIY thread HERE
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MOD EDIT: Personal attack removed

I thought that GL-5 based fluids should not be used in the transmission because GL-5 eats brass syncros.. Even though Mazda specifies GL-4 OR GL-5 fluids for the transmission, I've read that people have had transmission failures with GL-5 fluids.

Should a GL-4 fluid like MT-90 or Ford's XT-M5-QS Full Synthetic MTF...

I just changed my RX-8 with the XT-M5-QS fluid, and changed my dad's RX-8 with MT-90 back in May. Both run fine.. Should I have used the Eneos fluid? And the Eneos GL-5 won't hard the syncros in the tranny?

I think there has been a huge amount of discussion and (heated) debate on the issue. Lots of people on both sides of the fence if I recall. It's too confusing for me. At the end of the day, I totally trust Charles Hill/BHR. They make the best products for our cars, and have done extensive testing on various oils through Blackstone Labs. They've done all of the hard work for us! So if BHR recommends it, it's a good bet in my book.

This is interesting information worthy of filing in the back recesses of my alcohol-addled brain. I have been using MT-90 with moderate track use with success, but should that ever be less successful...

Charles still in charge! :ylsuper: