After reading your entire thread, other than the dealer screw up -- which can take a few fluid changes to correct, don't ask me how I know that -- it seems that really what you need is a fluid with better cold viscometrics than what came with your car. I've been driving manual transmission vehicles for my entire life, and living in Canada (albeit not regularly as cold as where you are), I've had cold shifting issues with almost every car I've owned except my current Benz C300 (which shifts beautifully in extreme cold, almost unbelievable really). I've also driven many VW's which seem to shift well in cold temps also. And the main difference I can see across the German brands rather than everything else is the use of very high quality and very THIN gear oil for the transmission. Also, they tend to use fluids with the most stable viscometrics, in other words, fully synthetic fluids with great basestocks that don't thicken up as much as the temp really falls. So what I would try and what I've had luck with in the past with my previous vehicles is to select the best synthetic fluid you can find and start trying them one by one until you find one that you like. Obviously you can't make up for shortcomings in the transmission design, but you can try to make it as good as it can be with the best fluid for the application and weather conditions. Redline MT-LV looks to be a great choice. Castrol also has some fully synthetic 75W manual transmission fluids that are available in Europe (I'm sure for a price you can have them shipped over). By memory they are Castrol Syntrans FE 75W, and Castrol Syntrans B 75W. You should look for the lowest Brookfield viscosity numbers for extreme cold performance, as well as lowest 40 C KV numbers. And don't worry about transmission failure, you will not cause any damage to your transmission. After all, it was already shipped with 75W fluid in it, so technically you're replacing it with another fluid of the same viscosity grade anyway (perhaps just thinner within the grade). Also, anecdotally, I can tell you that in previous transmissions that specified thicker fluid, I've used low viscosity fluids with great success and for hundreds of thousands of km's without issue or failure of any kind. Good luck and let us know how it goes.
Originally Posted by pleopard
The trade-off between protection and shift quality is an interesting one indeed and something I suspect may be a factor in this case. I guess we'll see - might take 5-10 years of otherwise trouble-free operation before I can conclude that. :-). Now, if I do end up putting RL MT-LV in and the transmission fails after a few years, I'll never know for sure if I should blame Toyota or RL. Haha. Seriously, all I can do now is laugh. Frustrating. It's not clear if it's an AW transmission. Toyota says it's their all-new design, but Toyota is so tightly linked to AW that it's likely AW.