Quote from chewbacca:
why do almost all luxury car makers require premium fuel when premium fuel offers almost no advantage over regular fuel?
Higher octane reduces spontaneous ignition. Spontaneous ignition is the cause of engine knock which can do significant damage to the engine over time.
Consider the extra $2.50 you pay a fill-up to be an insurance premium against your engine needing a replacement, which on luxury sport cars can be hand-built and cost a fortune to replace.
