...Have a 30 yr old weed trimmer and a chain saw that is at least 10 yrs old. Neither has ever had a problem running a 10% ethylanol blend. Never have had to replace fuel lines or rubber carb parts. Never have had any problems with any engine in any kind of eqiupment that had a problem the gas blend. The 10% blend is a non issue for me other than having a little lower energy content.
Talk to some of the chainsaw shops or loggers in your area. I know the shops around here have seen a large increase in problems with fuel lines and carb diaphragms and the like. Most of the established chainsaw manufacturers went to fuel lines that were more ethanol resistant years ago (I'm guessing anything made in the past 10 years, but I may be off on that by a couple years). The diaphragms may be a different story. From what I've heard it has been tougher to find a good, ethanol resistant replacement material for those.
I'm on a Forestry Forum quite regularly (
forestryforum.com) There are a a few guys on there from your area (Oregon / Pacific NW) who have complained about troubles, and even talk about getting gas from neighboring states when they are in the area.
Two things that can cause problems with ethanol gas:
1) leaving it in your saw (or gas can) too long. Ethanol will pull moisture out of the air and combine with it, eventually settling to the bottom of the tank. This is known as "phase separation". The ethanol water mix that settles out is corrosive, and has done a number on some carburetors. Also, since ethanol accounts for about 4 of your octane rating, you are running lower octane gas once phase separation occurs. Depending on what octane rating you started with, this can cause some serious problems with your engine.
2) E10 gas requires a different mixture setting than non-ethanol gas. If your mixture is adjusted for ethanol free gas, and you start running E10 without an adjustment, you'll be running leaner. You might be OK, especially if you were running on the rich side to start with... or you might over heat and lean-seize your engine.
The moral of the story... if you have to run E10 (which I will shortly be forced to do here in VT): get rid of the gas if it's more than a few weeks old. Run your tank dry if you won't be using the saw in the very near future (don't run that last bit out under load, however). Tune the saw properly to run on the fuel you will be using.