Most higher octane gasoline formulations also contain a greater number of cleaning additives. These additives are as beneficial as the greater octane.
At an indie shop recently I had a chance to see a 3.0L M103 engine with the head off, and couldn't believe how clean the combustion chambers were. The car had 375K on the odo, and the chambers looked like new.
I asked the mechanic, and he said the reason was frequent oil changes allowing good sealing, as well as constant use of good quality premium gasoline.
"No Italian tune-up required here, eh?"
1998 C230 "Black Betty"