[Healeys] High Octane Gas

[Bob Spidell]

re: "What else should I be aware off?"

IMO, you'd be wasting money (presuming the 110 sells at a premium to pump gas).  In general, you need only an octane 
rating that prevents the engine from detonation ('pinging').  Unless your Healey engine is running at, oh, 10:1 dynamic 
compression ratio or higher you don't need 110; i.e. if your engine doesn't ping now you won't notice much difference.  
However, the non-ethanol aspect is a possible advantage.

When higher octane rating was achieved with tetra-ethyl lead it was a bad idea to run too high octane gas in a lower 
compression engine, because the combustion temperatures were lower and allowed uncombusted lead buildup in the engine 
and oil.   With unleaded, high-octane gas that wouldn't be a problem but, except for a bit more performance to be gained 
from advancing the timing a little there's no real advantage.  Theoretically, you could run a bit leaner, but with 
carburettors that's problematic.  Dwell, etc. wouldn't change.

The TV commercials that imply--wrongly--that higher octane fuel makes a car run better are fraudulent, UNLESS your 
engine has an ECU, EFI, knock and other sensors and can 'tune' itself for the fuel's octane rating.  My Mustang, for 
instance, runs fine on regular (87 octane) but will produce about 10 more ft-lbs of torque in the mid-range on premium 
(91-octane R+M).  Note that's on a nominal 315HP/330lb-ft engine, so 10 ft-lbs ain't a lot (it does seem to run just a 
tad smoother with a bit less hesitation, but that could be wishful thinking on the driver's part).

Bob

On 7/28/2012 8:35 AM, Fred Wescoe wrote:
> List,
>
> I need some wisdom and experience from others on this.
>
> I have accidentally stumbled across a small supplier who sells 110 octane,
> non ethanol gas as a regular thing.  Not an airport, the local airport will
> not sell it to me.
>
> The question is, if I use it, will 110 octane fuel, in a standard Healey
> (68,000 miles, not rebuilt) engine, damage the engine in anyway?
>
> If I use it, should I tune the engine differently; IE timing, points, plugs
> or even change the oil more frequently?  I have a very old Sears tune up
> meter with which I precisely adjust points, dwell and timing so those
> things are not done by ear".  I also use a Color Tune to adjust the carbs.
>
> What else should I be aware off?
>
> Fred
> 63 BJ7
>
>


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Bob Spidell           San Jose, CA            bspidell at comcast.net

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