On Fri, 21 Aug 2015 02:35:40 -0700, therustyone wrote:

might depend on the car's sophistication. A quality engine will monitor
pinking and adjust the timing and fuel ratio to optimise burning with
the better quality (petrol anyway) it finds. An older car will just be
set to run on the worst fuel around.

Most modern cars will go down from a base map, if knock's detected.
But most are set to a 95RON base map. They won't go up from there.