In the new Equinox 2.4L engines there is a problem with them sounding like a diesel engine a bit after a few thousand miles of being new. Some people are also getting a knocking sound, and a loud clicking sound (clicking is the fuel pump due to the direct injection). I am not convinced the dieseling is a "problem", but I was experiencing it. I was also experiencing the loud clicking, and a bit of the knocking under acceleration.
So a few months ago I started putting only premium Shell into it (not any other convenient Top Tier stations around - man I miss the days of living near to a Kwik Trip, could also get 89 for the same price as 87 there). After a tank the "dieseling" started to go away, and the ticking is greatly reduced. Knocking is gone (I wonder if they programmed the knock sensors wrong for 87 in an effort to get the max fuel economy). Engine in general just runs smoother.
I've been noticing my wife has been going to a Thorntons station a lot lately because it is convenient for her. They have a guarantee that they'll pay for gas related problems, but of course it would be nearly impossible to prove their gas caused a specific problem. Recently I've been telling her to go to the Shell an extra block away. If there has been any difference, she wouldn't notice. And I don't drive it enough to know if it is making a difference or not.
I use fuel system cleaners in both regularly. Usually Valvoline. Might try Techron when I'm out of my stock of Valvoline ones.