The idea of octane level:
Octane delays the ignition of the fuel. So if you have 87 octane in a car it will ignite sooner than if you have 91 in a car or 94...
The lower octane level you CAN run in a car the more performance you get because the fuel is igniting sooner. However engines like ours need to build up enough pressure before the fuel can ignite and therefore our cars need 91 octane. If you put 87 in our car the fuel will ignite too soon and cause knocking and if you put 94 in the car, the fuel is not igniting at the prime time I.E its actually delaying ignition.
Also:
Quote:
Originally Posted by FricFrac
Whoa hold on guys - you are wasting your money running 94 octane. I was under the same delusion for a long time. You get more power out of lower octane fuel but we need to run 91 to keep the engine from knocking because of our high compression. 91 is optimum whereas 94 is only needed if your car is pinging or knocking and if your 370Z is knocking on 91 you have either bad fuel or a problem with your car.... unless of course your car is boosted then you're gonna want to run 94 or higher  |
One more:
Quote:
Originally Posted by kannibul
You are totally wrong, and 93 is not better.
Octane rating has everything to do with how slowly the fuel burns and how resistant it is to detonating under compression. Higher octane = slower burn/more resistant.
This is compensated by advancing the timing. The car is "programmed" to use 91 octane fuel, meaning the advanced timing is already active. Using higher octane gas yeilds no benefit as the car can't detect higher rated fuel. *(this is true of all vehicles!)
If the car detects knock, (either by detonation or by the fuel burning too quickly/early by using under-91 octane fuel), the car WILL retard the timing and enrichen the fuel map until the condition is minimized.
That said, it says PLAIN AS DAY in the manual to use 91 octane (or higher) gasoline (again, not because higher octane gas will increase performance, but because it's safer in the sense that it's less likely to knock/detonate), but in case of emergency you can use 87/89 octane, but do not fill the tank, do not drive the car "hard", and fill the tank with 91 as soon as it is available.
So, RTFM.
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