Originally Posted by JCL

I believe you, I just don't think you can attribute all of that difference to the octane/AKI rating (unless you have significant carbon deposits that are causing pre-ignition on the specified fuel).

The differences could be attributed to the oxygen content of the fuel, ethanol blend, additive package, or quality (most common). Apart from those items, some fuels just work better than others in specific applications. I do agree that you should find a fuel that works well in your vehicle. I would be interested in whether you have you tried a variety of 93 fuels, and whether there is any difference around town or on the highway, and in hot weather or cold.