Redline in a 6-speed for cold morning shifting, "test" results

[saaber]

Have used redline in other cars and it has made a vast improvement so I tried it in the Boxster 6 speed (73k miles) to improve cold morning shifts.

1) 75% redline 75W90NS, 25% stock fluid (not 100% because I pumped and filled via fill hole to save time) - Cold shifting improved immediately, notchiness in all gears increased

2) 90% redline 75W90NS, 10% stock - better cold shifts, more notchy all gears

3) 60% redline 75W90NS, 40% redline MTL (70W80) - about the same, maybe a bit more notchy

at this point I was very uncomfortable with the notchy shifting so I went back to 100% stock fluid

4) 100% stock. Surprisingly, cold shifting is excellent. Am very happy with lack of notchiness in all gears.

Conclusion: For this particular car, the stock fluid was much, much better than redline. So if you have cold shift stiffness on a 6-speed, I would recommend changing out the fluid and refilling with the stock fluid. It worked very well on this car anyway but I know others have had very good results with redline.