Porsche 911 Fuel Octane

Otherwise i would damage the engine longterm.
Porsche 911 fuel octane. I recently bought a 1982 911 and the pre purchase mechanic told me i hadto run high octane gasoline. Porsche gave me a card with a discount on 500 l of gas at. I only have access to 91 oct. Fuel system for porsche 911 1974 1989.
While reading the owners manual i find porsche recommends 91 ronor 87 clc octane. Belgian market porsches runs on 97 octane but we can get in some places 100 octane unleaded street fuel as well the perceptible difference is only the price in this case. The only times i use 94 octane fuel in my bs is when i go see my in law family. Octane hitched a ride with its original driver.
2008 911 carrera s sold 2009 cayman 29 sold. At the time this was the most powerful naturally aspirated unit that porsche had ever produced and remains the largest mezger engine produced for the 911 it fires into life with a menacing growl with that familiar gt3 rs chatter and rattle from the race spec flywheel aurally similar to its rsr stablemate. I would prefer to run 87 or 89 clc with 91 clcoccasionally. Mtbe was also anoctane booster.
I have used it and notice no performance difference and no knock. I have tried all the available combos and have not noticed any performance difference. Racing fuel is not recommended for street cars because of different reasons. The issue of fuel octane was a topic of discussion at the racing group trg tech session our region had there and the porsche trained engineers said there would not be an issue using mid grade 89 octane fuel.
Apparently nobody at porsche realizes that a good chunk of the usa technically does not meet their minimum requirement. The porsche 911 rsr finished fourth at le mans in 1773 and returned four decades later.