I have been using synthetic 2 cycle oil for nearly 10 yrs now without problems. The particular one that I use is a Pro-Mix that is used in handhelds that operate anywhere from 50:1 to 16:1 and until recently actually mixed at 40:1 [3.2 oz to 1 US gallon], now it has been upgraded to a newer synthetic oil that mixes at 50:1 [2.6 oz to 1 US gallon]. This oil is nearly smokeless but in some older machines it still smokes.
Yes it was at first hard to trust that it provided that protection I needed since nearly 2C handheld I repair is for a customer. It does however cuts the number of fuel mixes sitting around going bad. It even contains a fuel stabilizer that greatly reduces ethanol separation; still a good idea to shake the can up but using the fuel if it been sitting a while.
It should be fine to mix it at 25:1 if you feel uncomfortable using it as a multi-mix though it might over-oil things.
It would be interesting to find out from someone that uses this oil in the larger 2 cycle engines as the biggest I used it in is the 70cc class chainsaws.
