The problem with using higher octane fuel fuels is the risk of pre-ignition.

The most of the fuel additives that seems to be causing most of the harm to the equipment are the ones that the consumers are using them without following the instructions closely. I do use fuel stabilizers in my long term storage equipment of my own without problems as our fuel tends to go bad within a few months. Our fuel are nothing like it was when I was growing up. I use 2 cycle oil that has the stabilizer already in it and suffer no ill effects from the E10 fuels.

Most of the carburetor repairs that I do are on equipment that has sitting long term without use and the fuels simply dried up leaving the residues behind causing problems. I have used both OEM and aftermarket carburetor kits for the last 5 years in my business. Once these rubber parts are exposed to the fuels they will go bad no matter what fuel your using. It just depend how resist they are to the fuel.

The main problem I have with aftermarket kits is that some are not made correctly. It is one those gamble you take when buying aftermarket kits which is why I buy one of each on new applications to compare them. I only had one problem with a kit that was made in Brazil where the ethanol destroyed the gaskets overnight. Needless to say I don't use those aftermarket kits. I also have problems with 2 piece Flo-jet carburetor from Rotary as fuel mixture setup threading is incorrect but all do I is order that part of the kit from Briggs.

As for using carburetor cleaners most of my fellow techs here are now using ultrasonic cleaners with soap design for carburetor cleaning and water. The chemical drip damages to newer carburetor too easily. This is especially true on two cycle carburetors. Besides it not environmentally safe to use and is not good for our health either. As with any cleaning system it will not clean everything so there are times that other additives need to added to get the desired results.

Checking your fuel for ethanol is easy enough. Just use a measuring container that marked off in ml that is at least 150 ml. Fill the container with to a multiple of 100 ml. Now add about 50 ml of regular water. Cap and shake the mixture up. Wait a few minutes for the mixture to settle. The water and ethanol will combine and separate from the fuel.

The percent of ethanol will as follows:

100 ml of test fuel to begin with.
The fuel amount after separation equals 90 ml
then fuel contains 10 percent ethanol.