The synthetics run odd, and seemingly to me, not the same as castor, when in the 20:1 range. To the point, I may try to keep using 927 all winter, just, mix enough to use, and dump the rest in my vintage van. I truly deplore the hp loss, and the lean to me, tinny vibrations that leaner ratios bring with it. Not to mention, the whoops, I scored the cylinder! Remember, when your engine is up to operating temperature, it is beyond, a safe press fit, in the machinist world, thats how tight it gets in there! And our ONLY safe guard, is the very thin film, of oil. The micro second that it goes, so does the motor. The real world, NOTHING actually touches anything else, until, it bonds. The repair shops, they love this fact? Yes, the Yamalube "r" synthetic, is marketed by every oem, and is as good as any other synthetic, super M from Maxima included! But for a 2 stroke race engine, nothing will perform like a castor oil, not castor based, synthetic, IMO! And even though, you may be slow in the trails or track, the second you wind it up tight, then you are in the racer world, that the engine was designed for, just not for too long! I had the pleasure, of being on the same track, with Todd DeHoop, he was on a YZ125, on the Redbud track, wound up TIGHT! After his 3rd 15 minute practice, he switched to a KX250. I do wish, I would have caught up with him in the pits, to ask what ratio he was running. It smelled like race fuel, ether based, and the oil, was different, than I am used to, no 927 or Xamax. Track talk with pit dads, they are for the most part, floundering, BIGTIME, blendsall and some magic in a bottle, C-12 and speedways best out of the ground tank fuel mix, and a blown motor, and soooo much vibration, I truly feel sorry for the rider!.