Replies

1. 
   frenchy | Nov 22, 2009 08:40pm | #1

   Unless your car calls for it using higher grade than 87 octane is a waste of money. The cars which call for hiigher grades are cars with extremely high performance engines such as the new supercharged Corrvette, Certain European Imports and turbo charged cars etc..

    Higher grade fuel does not make more horsepower! (in fact if you put  a engine designed for 87 octane on a dyno you'll find high octane fuels decrease power)Nor will it get better fuel mileage etc.. Or run longer or better etc..

     What high octane does is depress the flame propagation rate so that preignition doesn't occur.. (Engine Knock)  A side effect of high octane gas in an engine designed to ryn on 87 octane is that the egt.. (exhaust gas temp ) is higher because some of the flame is still burning when the exhaust valve opens.  As a result the temps downstream will be higher than designed for  causing exhaust manifolds to warp and catalitic converters to oveheat and clog..

    There is a way to use high octane fuel to your advantage if you have E85 gas available (and only with E85!)

     E85 is 85%  ethanol and a lower (much lower) grade of gasolene. Because it's alcohol 85% of it has a 114 octane rating so you can see how low the grade of gas stock is added to drop it all the way down to it's octane rating of 88.

    However one of the properties of gasolene is that a remarkably little octane enhancers results it an astonishing increase in octane..  So if you add 94-97 octane gas back into the E85 you could wind up with an octane of over 100.

     Now only custom built engines are capable of using more than 100 octane gasolene without an actual decrease in power.  

    Since it contains so much alcohol it's not even good for vintage engines because those carburators aren't jetted rich enough nor are the gaskets usually up to handling the alcohol.  The engine wil see the alcohol as too lean and start to backfire indicating a too lean a mixture.  meanwhile the gaskets in the carburator will swell up and start to  leak.

    So forget it forget modified E85 for all those vintage muscle cars of the 60's etc.. (unless you up grade the whole fuel system including the fuel pump and rubber lines)

    

     

    

1. 
   BoJangles | Nov 22, 2009 10:43pm | #2

   Right on Frenchy !!

2. 
   McDesign | Nov 23, 2009 01:57am | #6

   All the street car guys in horsepower competitions on the portable chassis dynos use E-85, 'cuz it's a "pump gas".  Some pretty amazing horsepoer figures are possible, but with fabricated injectors - even at 100% duty cycle, passenger car ones won't flow enough, especially with alcohol.

    

   Forrest

2. 
   Piffin | Nov 23, 2009 12:26am | #3

   always is a long long time you know.

   I am guess that is somewhat to do with inflation, but more, that now we have up to 10% alcohol added to the gas we buy, the cost ratios of the two blended effect the price more.

   now that I read that back, it makes less sense than while it was just a thought bouncing around inside my empty skull.

    

    

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   Taunton University of Knowledge FHB Campus at Breaktime.
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1. 
   Sphere | Nov 23, 2009 12:35am | #4

   Geezuz. I was still masticating what the frency said, and then you plop that pie out there..I hope yall aren't contagious.Spheramid Enterprises Architectural Woodworks

   Repairs, Remodeling, Restorations

   PROUD MEMBER OF THE " I ROCKED WITH REZ" CLUB

    

1. 
   Piffin | Nov 23, 2009 01:33am | #5

   don't over eat and you'll be OK come morning!First third of frenchies sounded pretty good, then the pages fell out of my frenchy translation guide. 

    

   Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

1. 
   frammer52 | Nov 23, 2009 02:52am | #7

    frenchy translation guide>>>>>>>>>>>>>>>>>>

    

   Could you post that so the rest of us can view!>G<