Mixing synthetic, regular MT fluid?

[JC_VT25]

I am considering mixing Redline MT90 with standard MT GL4 fluid in my Mazdaspeed3. While the synthetic should help reduce wear and increase hot performance, there have been some reports of very poor cold weather performance as well as some concern for friction modifiers for the LSD. The mix seems to be a middle of the road compromise. Anyone think of a reason not to do this?

 

[mechtech2]

REdline 75-90NS is GL5 and should be better for the limited slip.

 

[JC_VT25]

Mazda specs GL4....some problem using GL5

 

[JC_VT25]

Redline MT90 is GL4, not GL5

 

[RD400]

Well, you could mix Redline MT90 and MTL if you're looking for better cold weather performance. They are both GL4 and similar chemistry.

I wouldn't mix different brands together. Redline also has a friction modifier that you can add separately for the LSD.

 

[Spector]

I have been running a 50-50 mix of MT90 and MTL for a few years now, much better cold shifting and fine all year round.

 

[JC_VT25]

While the MT90/MTL mix has some appeal, MTL doesn't meet the weight spec for Mazda, and I'm more tempted to go with a non-synth 75w-90 for the mix (partly because I'm going to have my Mazda dealer do the change).