Could someone explain how a higher octane affects engine performance? I always use either 91 or 93 octane in my 540s. I was wondering how the use of a higher octane fuel such as 101 or 110 would affect performance? My compression is 10.25:1. Any comments appreciated.

Higher Octane is not a power adder. Any higher then what your engine needs in order to avoid preignition (knock) is a waste.

in a nut shell: octane rating is a measure of the resistance of gasoline to autoignite.

Higher Octane is not a power adder.

But it sure does help with detonation

If you don't have any detonation issues running 93 octane and switch to 100+ octane, you will most likely loose some HP and have a sooty transom.

That saved some money, thanks for the replies!

Actually running a higher octane fuel than the engine requires (once you get into race fuels) can actually hurt the performance of the engine, and in extreme cases hurt the engine itself due to the burn rates of the fuel and what it is designed for.

On my Scarab blower motor we dynoed with 93 and tuned it there, Made one pull on race gas 704 specific gravity,it picked up 25ft TQ no hp gain anywhere though.

My Chevelle we dynoed it on 93 ,10.7cr,never tested it on race gas, When I put race gas in the tank its allot more responsive,idles better ,it just cleans it up,Ive ran at the track both ways and cant tell much diff,but no back to back runs to see though. Usually at the track I put race fuel in it for safety(detonation) and also running Nitrous


Ive been told that if your motor doesn't need the octane it will lose some power, It depends on the blend of race fuel,some are fast and some are slow.Like the NOS red fuel is a slow burn fuel, its more forgiving and tunable.I would think the faster burning fuel blend would be close to the pump gas as per HP.Water specific gravity is .83 most pump gas is .730-.760.race gas is around .720-.700. The race gas I used on the Blower motor was .704


You can advance ignition timing to try to recover power, but that will cause the air/fuel mixture to burn earlier in the crank stroke and spend, percentage wise, more of the energy produced by the expanding, burning mixture, pushing back down, trying to prevent the piston from rising up to the power stroke - robbing power.



If you could find MTBE a chemical to oxygenate your pump gasmethyl tert-butyl ether (MTBE)
http://www.eia.doe.gov/emeu/steo/pub...e%20oxygenates

Also remember that MTBE is a disagreeable compound,your flexible organic rubber (hose) meltsand illegal now

octane boost
In the old days, TetraEthyl Lead (TEL) or TetraMethyl Lead (MEL) was added, with TEL being the most common in the United States. Now, as leaded fuels are not allowed to be sold in many areas, other, generally more expensive and less effective as compared to cost, fuel additives are added. Lead was an extremely effective knock suppressant.I don't think you can get TEL,TML and MEL,

Also most race fuel 110 octane or higher they put lead in it.

The lead replacement now is made by Ethyl Corp.Its called Magenese tricarbonyl (MMT).Adding Magenese to 93pump gas will only get ya to 95-96 octane.In 2004 they claim that Canada is still putting it in the pump gas to raise octane.

some info http://toxics.usgs.gov/definitions/fuel_oxygenates.html