I've ran Redline SPH since my 1000 mile service (now have 8000 miles). However, after joining this site and reading all the rave review of the Spectro 6-Speed tranny fluid, I decided to give it a try a few weeks back. I especailly liked the fact that Specto rates it as a GL5 fluid, whereas Redline doesn't rate their SPH. Anyway, not to be a hater or anything, but I really think I like the Redline SPH, mainly for 2 reasons: Noise. There seems to be a greater amount of "slop" or "slack" in the tranny with the Spectro fluid that wasn't there with the Redline SPH. Kinda like when your on the throttle, then let off, and get back on it. Perhaps the thicker SPH provides more "cushion" than the thinner Spectro..??.. Lurching. I start my motor with the tranny in nuetral. Like many others, my bike lurches forward a little when I put it in 1st gear. But the lurch seems to be more significant with the Spectro than the Redline. None of these are really deal-breakers, but I'm not as excited about the Spectro as I was before I actually tried it. Many here strongly support the use of this Spectro fluid, even over the Redline SPH. I guess I did it expecting to find a little positive difference, but instead I've noticed a little negative difference. But I'm still left wondering if the Spectro, being a GL5 rated gear lube, is still better for the tranny than the (unrated) Redline Shock Proof Heavy..??.. Just my opinion that I wanted to share in case anyone else is in my situation.