Anyone think it would be an issue to mix Honda MTF and Redline MTL fluid? I happen to have a bottle of each and it has been about 15k miles since last change. The car doea see some track time.

 

I wouldn't. No urgency to changing the fluid. Just wait and get more of one brand.

 

I don't think it's a good idea

 

There's a potential that the different additives used in the two MTF's can cause issues when mixed together

 

Redline MTL is a bit thick, it works best in high temp use and it is a great fluid, the Honda MTF will thin it out though as it tends to be quite thin. But as mentioned by Afzan you really don't know if the friction modifiers in the two fluids will be compatible, the friction modifiers in Redline MTL are a very specific formula for synchronizer speeds. Only way to tell is to try it and report back, you can be our little guinea pig

 

I've never used those 2 together, but I have used honda mtf and redline lightshock proof in high hp severely abused b-series trannys before with good results.

It wouldnt cause any issues but mixed fluids dont typically last as long as non "mixed" fluids do.