When I bought my Cobra, everything was original factory, including the trans fluid. The T5 shifted okay, but it was unpleasantly notchy and didn't like finding first at a stop light when hot. When I tore it open to replace the 8-tooth speedometer drive gear with a 7-tooth gear for more ring and pinion choice options, I refilled it with Royal Purple MT fluid on a recommendation from a friend who uses it with heavy machinery transmissions. I also contacted Royal Purple directly to ask them if I should use their ATF or MT fluid for a T5. They said to use the MT fluid and that it already had friction modifier in it, so I didn't have to add any like you do for the factory recommended ATF. This was the first time I've used Royal purple for anything and I was skeptical, especially at the $17 / quart price tag at the time (it's probably way more expensive now). However, I was blown away by the difference. It's very noticeable. It feels so much smoother after switching. It's notchy, but in the good smooth notchy way you want from a muscle car manual transmission, and the resistance to find first gear when hot has completely gone away. I never would have believed that the fluid choice could make such a difference, but it does. Maybe my factory fluid was just old and warn out, but the improvement in shift quality / feel is completely worht the extra $$ in my experience.
