Date registered: Dec 2005
Vehicle: W211 E320 Bluetec R129 SL500 - $1300 car ........ Ford F350 6l
Location: CA Bay Area
Mentioned: 9 Post(s)
Quoted: 1057 Post(s)
OK I try to answer it again.
Modern engines do have anti-knock sensors for EMERGENCY running on lower octane, but why do you buy performance car to kill the performance in the first place?
On practical use, I did own lot of cars in my life, running on lot of fuels, including 100 octane available in Europe.
With my experience, when I was driving Volvo design on regular, for mountain driving I was fueling up with Premium at the time when Premium cost 25% more than regular.
Thanks to better fuel, while taking long grades the 4-cylinder could make most of them on overdrive, without hassle of downshifting and slowing down.
It is not definitively proven that lower octane can damage the engine, but check how much rebuilding the head on your engine can cost you? Just think about the risk.