Quote:
Originally Posted by imag
I understand the benefits of oxygenation as well as energy density. However, it is not uncommon for modern high performance moderate-high compression motors (like ours) to have small amounts of detonation with 91 octane gas, especially when the motor is hot and/or the air is hot and dry. Likewise, they can adjust the timing to can take advantage of moderately higher octane fuel (94-96) when conditions warrant - like being on a dyno or on a race track.
Edit - sorry - missed the second page. RCZ is exactly right.
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I think that the Z is built on spec for 91 octane to run properly under all conditions, and as a safety will retard the timing if it detects a knock.
Gas that is delivered to the gas stations are "more or less" 91 - so some days you might be pumping in better than 91, other days less than 91. Depends on what gets delivered from the supplier.
If you doubt it, look at the sticker on the pump where it was tested.
Soemthing also to consider for those who top-off often. There's fuel in that hose all they way from the pump - that's about 1-3 gallons worth of whatever was put in there by the last customer. So, the first 2-6 gallons you put in are more than likely "mid grade" - 89 octane...even if the gas in the tank is on-spec, you won't reach a perfect 91 octane even if you fill up...
