Brian,
this is an extension of this discussion-maybe people can read it so they understand what you are looking for in this thread
http://forum.ih8mud.com/80-series-te...preme-gas.html
The OM says,
Select Research Octane Number 91 (Octane Rating 87) or higher.
Use of unleaded fuel with an octane # or rating lower than stated above will cause persistent heavy knocking. If severe, this will lead to engine damage.
If your engine knocks..
[steady knocking while holding speed on level roads, see your dealer]
However, now and then, you may notice light knocking for a short time while accelerating or driving up hills. This is no cause for concern.
lexus recommends use of gasolines that contain detergent additives to avoid build up of engine deposits.
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I look at the knock sensors opposite- you can run lower octane for similar performance.
9:1 compression ratio-
I always thought of this not as "high" or "low" but rather as an efficient ratio for a gas pass. vehicle engine.
For 87octane, 9:1 is pretty efficient. If you go lower than it looses thermal efficiency. I think most cars are around 9:1 (?)
another factor is that the 1FZ is not a high revving engine. It develops all its power low.
Compared to Toyota's modern truck 6 cylinder- the 1GR - which has 10:1 yet runs regular pump gas great, about 50hp more, 2x the mpgs and ULEV 2
I honestly feel it is not economically advantageous to run higher octane fuel, but to do so if your engine requires it (knocking) or you are boosted.
just my thoughts