I'll try and keep it simple for you ... Yamalube is made by citgo,, citgo makes a dozen different packages for the same oil!!!20.00 a gallon for yamalube and 7.00 a gallon for walmart oil... THE EXACT SAME STUFF!!! THE OIL HAS ALMOST ABSOLUTELY NOTHING to do with powervalve cleanliness!!!! MORESo your JETTING and driving habits!!!!! LOAD AND HUMIDITY also have a MAJOR EFFECT on powervalve cleanliness!! i wrote a DOXEN articles on this and apparently NOT MANY of you read OR COMPREHEND what you read.. A few of you guys HAVE CHANGED to synthetic oils and I COMMEND YOU!!! the others,,,,,well,,,,,