Is Yamalube synthetic? I'm certain the last stuff I bought was regular TC-W3, several years ago. My understanding is that petroleum based oils will mix OK, but you don't want to mix them with synthetics. On several occasions, I've used other than Polaris oil in my XLT in a pinch. Yamalube(at least the TC-W3 I bought) mixes OK with Polaris, and a quart of Castrol TC-W3 from a store in the middle of nowhere caused no problems.