I'm using Mobil 1 in the tranny and have no problems yet. I don't get any grinding at all. I ground the gears a couple of times, but I think that was a product of the new clutch, and me not being used to it. I haven't done it since a couple of days after I put in the clutch. I have about 3k with the Mobil 1, and at this point I would recommend it to you.