Just a thought, with all of these "which oil is the best" post we are having, at about $300-$400 on average from a commercial grade trimmer and most of them lasting at least 3 years on even the cheapest oil aren't they kind of a disposable product?? I mean if it last 3 years (or $100 per year) haven't you gotten your moneys worth out of them? I take good care of my equipment, very good care. I have 4 trimmers and 3 blowers (chain saws) which have never given me any problem using multi-purpose Mercury Quicksilver oil. I just can't justify loosing any sleep or going out of my way to try to get the "best" oil, which ever one that is. It is apparent to me that most two strokes that use one of the better known oils are going to last a long time on "average". I must note that the only reason I'm using the Mercury oil is that I have always had a boat and it was readily available and states that it is suitable for any air or water cooled two stroke. I don't recommend going out and buying it just for air cooled equipment. I just have a surplus of the stuff. Anyway most of my trimmers last much longer than 3 years and they are just not a high dollar item compared to much of my other equipment. When it comes to my ZTR's engine, hydraulics or even my trucks I am completely opposite. I want some of the best oils, filters, greases etc because I have a lot invested in them. I really take maintanence seriously on more expensive items but a trimmer, even if it last only 3 years has paid for it's self many times over. And most last much longer. At $100 dollars or less a year I "almost" consider them disposable. When I run out of my current supply of multi-purpose oil I will switch to a reputable 2 cycle oil for air cooled engines. Not sure which one yet. If you are under warranty by all means use the right oil!