[QUOTE] I have. ZXR750R, Mobil 1 4T. And if anyone can come up with a reason why the oil wasn't the cause, though the slipping started when I changed to fully synth and stopped when I changed back to mineral a week later, I'd love to hear it.[/QUOTE] Sure - as I said, other people have definitely reported this, and, most often, with Mobil 1.