unitedwestang

There's no myth about it. Its a combination of physics, fluid dynamics, and thermodynamics. It can be quantitatively determined what is best suited for an engine. The engineers from the factory do this, thus the suggested 87 octane rating for most vehicles from the factory. Anything higher is simply not needed. Plain and simple. No speculation. No mythological engine fairies making your engine run better.

Personally, I would be more worried about the ethanol and other additives in some gasoline than trying to run a higher octane...

unitedwestang

I will say, however, that on a small percentage of high mileage vehicles it may be necessary to step up an octane grade to avoid ping or knock. Over time a car may develop carbon deposits in the engine effectively increasing the compression ratio and sometimes creating "hot spots" leading to predetonation. This would emit an audible ping or knock. Should this happen you may want to increase octane.

HOWEVER. This increase in octane is only the band aid fix and not the cure of the underlying root cause, and I believe this can be largely avoided by wisely choosing your fuel and proper vehicle care.

Let me be abundantly clear in this: If your vehicle is currently running fine on the recommended octane level from the factory (vast majority of vehicles), and your vehicle is NOT tuned for a higher octane there is no reason your vehicle would see an increase in performance from running higher octane fuel.

Additional point to be made though:
In vehicles equipped with knock sensors, the ecu can advance timing to a certain degree to attain maximum engine output--as it would do in the case of running higher octane. This, on the base level, is what is essentially done in a tune--increase spark advance to account for higher octane fuel. However a stock tune can do this only to an extent and I can only imagine the increase in performance would be minimal if at all noticeable.

99GTvert

Do you have anything to back any of this up?

bluebeastsrt

Hmmmmm OK?

audioAl

The 3.7 Cyclone DOHC has variable timing and can tell what octane the car is using. Also, the HP changes from 305 with 87 octane to 315 hp with 93 octane.

potman

My manual specifically states that for the 4.6 v-8, it will run OK on 87 octane, but for best overall performance 91 octaine or higher is recommended.

Gt04

Cuz race car

WhiteFoxGT

i still stand behind my statement on post #8

try that and post results please

wardNM05

there is no point in running 93 unless your car is tuned for 93