My dad has used the standard 40:1 in his Lawnboy for over 40 years. I've used Ultron and now Amsoil synthetic 2-cycle oil, mixed 100:1, in my chain saws and trimmers for 25 years. I have yet to wear one out. I have never even had to replace a spark plug.
If you run synthetic 2-cycle oils in the ratios specified for mineral 2-cycle oils, you probably will not even be able to start the mower, trimmer, or chain saw. You will likely pull your arm out trying. Synthetic TC oils are thicker than mineral-based TC oils, which have a heavy solvent component in them to reduce carbon buildup on the cylinder head, rings, exhaust port, and muffler.
My TC equipment is so reliable that I no longer believe in buying quality Echo products. My $78 Weedeater from Home Depot works just as well and is just as reliable as my Echo was. I attribute it to using API TC-rated (air cooled) synthetic oil. Also, my equipment gets used a lot. I knew a guy who had his own landscaping business in Florida. He didn't even really measure the synthetic TC oil he added to his gasoline. He filled the bottle cap and just poured it in. I was shocked, but he never had any trouble.
[ July 15, 2005, 09:11 PM: Message edited by: TxGreaseMonkey ]