It's like farting in the bath tub I guess..... you see something, but nothing happens other than it smells like B-sh** Now we know Shells 30 year off shore secret!
All I know is that if I am desperate and forced to use Shell, I get about 100 km less to the tank than if I use PetroCanada. Even ESSO (Exxon) is better, but not by a whole lot. Ma's 81 Volvo would not idle on Shell or Esso, and would not start at all well in winter on Esso. One time I was faced with one or the other, nothing else available. I chose Esso as the lesser of the evils, and very nearly had to have the car towed as it simply would NOT start!
i use a gas with 10% ethanol and i put 1 caps or 2 of two cycle motor oil in the tank when i add gas in my car, my 41 dodge run great like this since 3 yrs now, i think the oil protect the leather of the pump maybe it's a wrong ideas but i do that, advise of an old mechanic.
The other problem w/ethanol mixes is it's really lousy for anything that sits a while-much worse than older gasoline. I bought a used generator at a auction last year and had to rebuild the carb because it was all gunked up. My neighbor saw me doing that and then somehow I ended up rebuilding the carb on his Honda quad and his generator! I wonder how many generators, pressure washers, snowmobiles, mowers, etc are messed up from it?? I'm a real believer in Stabil or Sea Foam,etc- Both seem too work good.