[Guillermo]

Once I get better at double clutch heel and toe I'm going to dispose my transmission oil (remove the debrid from a few misshifts..) and replace with Red Line MT-90 synthetic trasmission oil.
I'll switch in the early spring.

 

[Sparky5501]

I would be mindful of using Redline. It is much thinner than standard synthetic gear oil. More similar to Automatic tranny fluid in viscosity. I've used it in some of my manual transmissions and have always noticed weeping from the seals. The Insight is a new enough vehicle to maybe not have this problem but I would check periodically just in case. Other than it being slippery enough to leak out seals, Red line is pretty tough stuff. Plus, it has a great cherry smell, no kidding!

BTW: I've used Swepco tranny fluid with great success in my other cars for track and street.

Haven't had the need to change the tranny fluid in the Insight for myself. I like the idea if the dealership getting dirty and disposing of the old stuff. And all i got to do is drink coffee and watch a little TV in the lobby. I guess I'm getting lazy.

 

[cakley]

Keep me posted on how the redline oil work out for you.

 

[Insightful Trekker]

<snip>

and replace with Red Line MT-90 synthetic transmission oil.

If i remember the MT-90 is supposed to be full range synthetic up through 90W. And as I recall it will cause stiff shifting in a Honda that is designed for the 40W range.


I've used Mobile1 10w-30 in my old CRX HF (200K+ miles) and now in my Insight (25K miles) without a problem. Although I believe there is an "official" Honda warning of some type on the subject. As I remember it is in regard to being too slippery and the synchros not grabbing correctly causing gear rake on upshift.

 

[Guillermo]

in regard to being too slippery and the synchros not grabbing correctly causing gear rake on upshift.

Yes, I had that problem with my previous car (1998 Subaru Legacy GT).
The owners manual said to use 90W gear oil in the manual transmission.
So I put some 90W Castrol synthetic gear oil in hopes to improve winter shifting. Over a matter of weeks the shifting became more difficult because the syncros were slippping too much. I replace it with cheap Castrol 90W gear oil and the shifting improved.

I later read that manual transmissions require some friction additives so that the synchos will work properly. I bought 4 Liters of Red Line MT90 for my Subaru but sold the car before I put the stuff into it.
Red Line MT90 is a synthetic manual transmission oil specifically made with special friction additives to improve shifting performance and reduce wear in manual transmissions compared to much cheaper OEM fluids.

http://www.redlineoil.com/redlineoil/mtlti.htm

You are right the MT90 is too thick for Honda transmissions.
Red Line MTL is a much better choice.

I'll try to sell my MT90 and buy some MTL instead.
I'll let you know how it feels in a few months (it's too cold for me to physically change it anytime soon).