----- Original Message -----
From: "Robert Barber" <rbarber41@hotmail.com>
To: "Military Vehicles Mailing List" <mil-veh@mil-veh.org>
Sent: Saturday, October 27, 2001 5:59 PM
Subject: Re: [MV] X-ref parts for MULE request
>
> Keith
>
> >You have a good idea, but I'd worry that the higher octane would burn
> >pistons,valves,etc. Let me know if you have any adverse effects.
>
>
> Higher octane rated gas burning internal components is an
> old wives tale and bogus .. You can burn / destroy internal
> motor components via a too low octane rating (detonation)
> or via the new low lead formulations that can and will cook
> valves in some motors ..
>
Bob is absolutely right, it really is an old wives tale because some people
have put 2 and 2 together and come up with 5, we have been here before.
The documented instance is the Sherwood Foresters running their jeeps on
AVGAS during the Italian Campaign, they all expired after two weeks simply
because the TEL levels in this fuel corrodes the valve stems away unless the
aircraft special alloys (21-4N) of the time (but standard stuff now) were
used. The original materials used were intended for zero or very low lead
levels, exhaust valve burning was commonplace unless the quite short
head/valve service intervals were observed.
The use of higher octane than is needed is simply a waste of the fuels
potential, old valve steels whilst being happy with the high TEL content
making gobs of molten lead salts to lubricate the exhaust seats will have
their stems corroded quite quickly.
> If you could still find Aviation "145" colored purple
> (WW II - 50's prop fighter fuel) you could still run it in a
> 8:1 compression motor with zero adverse effects.. Its when
> you go the opposite way you can get in trouble quick..
>
Quite so, the octane rating is derived simply by the use of two fuels in a
lab standard, variable compression test engine, one with zero rating and the
other with 100 oct rating, the ratio of these to produce the knock point at
the same compression setting as the sample gas/petrol is the octane rating,
after 100 oct the numbers represent the milligrams per gallon of TEL added,
so 145 oct has 4.5mg/gall of TEL.
Propane actually has an octane rating well over 100 but can be found
powering all manner of low compression engines working contractors small
plant and millions of fork-lift trucks. None of these are performance
engines and have CRs below that of the average domestic car, they run for
years of course.
LPG - propane conversions on LR 101s are very popular here because of the
savings to be had and the vehicle affording easy LPG tank fitting.
Richard
Southampton - England
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