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Well a couple quick things. The 1FZ is not high revving, but this is not about WOT. The ignition tends to advance the most at lower rpms and higher throttle, such as accelerating from 20 to 50 mph. This is my observation at least. The 1FZ is a very hard working engine, because it has to pull a 3 ton vehicle from 0 up to 60 or 70 mph and that takes plenty of energy. Even under normal throttle, we're talking more h.p and more torque than most Honda's peak out at. I'm not suggesting that the engine is stressed by any means, but that any differences at WOT and higher rpms will be affected at lower rpms under normal driving conditions as well.
If the engine is compensating for the 87, then it appear to run OK, but its not running at its peak and its not likely taking advantage of whatever extra energy is available in the lower octane fuel. If the engine was not compensating was allowed to run on the edge, just above the point where damage would occur as another thread suggested some races engines do, then it probably would run better on lower octane fuel, but more than likely Toyota engineers have compensated the engine to keep it as far from knock as possible on 87 octane. We don't know at what point the engine compensation kicks in on 87.
If the 1FZ was designed to run its peak on 87, then 87 would not be the bare minimum and I'm glad you posted that info out of the owner's manual, because I was going do to the same thing myself to illustrate that Toyota calls 87 the bare minimum. Had the 1FZ been specificly designed mechanically and electronicly to run on 87, then it should be able to run on even lower octane fuel under normal circumstances, just fine, but with lesser performance as the engine compenstates. What Toyota is saying that the 1FZ is only designed to compensate down to 87 and under certain circumstances, such as extreme loads, heavy tower, long steep grades combined with extreme heat, it's no longer able to compensate and would require a lesser knocking fuel.
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