We all have our favorite valve oil. During one of my sessions we got into a wild discussion regarding valve oil and which one is the best and WHY. Many of us are now using synthetic valve oil such as Ultra Pure, which I have come to love. Many still use the petroleum based oils like Al Cass. Of course on older instruments it is best to use a heavier oil such as Holton's Rotary Valve Oil. I would like your opinions..constructively..on which valve oil you think is the best and WHY. Thanks and I look forward to your comments.