Yes,i think i most had discuss this matter with many people.

Our VX's came equipped to run on 87,ok that's fine & for the 1srt three months i use 87 & i didn't like the way how the engine performed at all.

And since i began to use 93 my engine runs smoothly,the knocking that my VX had from day 1 is much less louder,plus the mileage is way more then with 87 so my advice : USE 93 at all times or at least as much as you can afforded.

Another key in the puzzle is the way you drive,that guys have a lot to do with the mileage you can run for each gallon of fuel you use.
I personally don't press deep the gas pedal to move foward,plus the acceleration our VX's comes with is enough to move fast the almost 3000 pounds the VX weights.
My secret : press the gas pedal little by little,the VX begins to gain speed & in 7 seconds the VX is moving at 30 mph; What more you want ?

Since the engine comes with the variable valve timming feature which means that the engine would use only the amount of power demanded by the throttle & save fuel for when the driver demands more power.

Again,use 93 as much as you can afford,plus the 93 is a cleaner fuel & produce less polution because it burns slower then the 87,the fuel lines remains much cleaner & all related components.
Add twice a month a fuel injection cleaner & you'll feel the difference with the engine.

This is just my two cents quote