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Camarotobeornottobe · 09-10-2014, 02:09 PM

So, I wanted to report back for everyone's benefit.

My conclusion from research:

I concluded that mixing D4 and MTL 50/50 would be okay. I came to this conclusion based on communications with Redline, Tremec, forum members who had used MTL, Corvette TR6060 results, and a few speed shops (including JRE, which HIGHLY recommended going straight MTL). After all, we are only talking about raising the viscosity slightly when doing this mix, with the cold viscosity going from 34 to 44 cSt, and the hot going from 7.5 to about 9.0 cSt. The two are basically the same GL-4 synthetic fluids with one just being slightly thicker. Research also points to the manufacturers "requiring" the thinner ATF in order to minimize effort needed when the tranny is cold. Since my car will rarely be driven in the winter, it was less of an issue. Research also indicated that thickening the fluid would quiet down an otherwise noisy tranny.

Results:

I put it in when the weather was 85 degrees. My first reaction was WOW. The shifts seemed smoother and the tranny quieter. So much so, I almost regretted not going 100% MTL. But, I waited for some more thorough driving.

Now, I have been driving around about a week. At all temperature stages, the tranny is considerably quieter than at the same temperature with straight D4. By that I mean, it still gets louder when the fluid gets hot and thinner, but always quieter than the D4 was at the same temperature. To be clear, by "louder," I'm talking normal TR6060 gear noise, not a mechanical problem.

Importantly, when warm, shifting is noticeably smoother than with D4 alone (which was already an improvement over the OEM fluid). I am confident it is protecting the tranny better at these higher temperatures.

I purposely drove the car at cold start-up without letting it warm up. We have had a couple of 60 degree mornings, though my car was in a non-heated garage that stayed around 70. Shifting was slightly stiffer when cold, but only marginally so and only for the first couple of shifts. Obviously, the real test won't be until the dead of winter. However, while my car won't be officialy stored during the winter, it won't be driven much either. So, any downside to using some MTL should be mitigated.

Bottom line, I recommend doing the mix. Hope this helps others.

09-10-2014, 02:09 PM	#20
Camarotobeornottobe Drives: 1LE Join Date: Feb 2013 Location: East Coast Man Posts: 550	So, I wanted to report back for everyone's benefit. My conclusion from research: I concluded that mixing D4 and MTL 50/50 would be okay. I came to this conclusion based on communications with Redline, Tremec, forum members who had used MTL, Corvette TR6060 results, and a few speed shops (including JRE, which HIGHLY recommended going straight MTL). After all, we are only talking about raising the viscosity slightly when doing this mix, with the cold viscosity going from 34 to 44 cSt, and the hot going from 7.5 to about 9.0 cSt. The two are basically the same GL-4 synthetic fluids with one just being slightly thicker. Research also points to the manufacturers "requiring" the thinner ATF in order to minimize effort needed when the tranny is cold. Since my car will rarely be driven in the winter, it was less of an issue. Research also indicated that thickening the fluid would quiet down an otherwise noisy tranny. Results: I put it in when the weather was 85 degrees. My first reaction was WOW. The shifts seemed smoother and the tranny quieter. So much so, I almost regretted not going 100% MTL. But, I waited for some more thorough driving. Now, I have been driving around about a week. At all temperature stages, the tranny is considerably quieter than at the same temperature with straight D4. By that I mean, it still gets louder when the fluid gets hot and thinner, but always quieter than the D4 was at the same temperature. To be clear, by "louder," I'm talking normal TR6060 gear noise, not a mechanical problem. Importantly, when warm, shifting is noticeably smoother than with D4 alone (which was already an improvement over the OEM fluid). I am confident it is protecting the tranny better at these higher temperatures. I purposely drove the car at cold start-up without letting it warm up. We have had a couple of 60 degree mornings, though my car was in a non-heated garage that stayed around 70. Shifting was slightly stiffer when cold, but only marginally so and only for the first couple of shifts. Obviously, the real test won't be until the dead of winter. However, while my car won't be officialy stored during the winter, it won't be driven much either. So, any downside to using some MTL should be mitigated. Bottom line, I recommend doing the mix. Hope this helps others. Last edited by Camarotobeornottobe; 09-10-2014 at 02:27 PM.