Fuel Additives (Gordon Millar article)

Gordon Millar has written tech articles for Classic Boating Magazine and numerous other publications for many years. I've used his recommendations on various projects over the years, and I want to share the following article as a point of information. It was written for an older series of boat than our Commanders with their "mid 1960's power" but much of this may still be applicable. In any case, it is a paper from an exceptionally well informed engineer.

Paul



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Immediately after World WarI I worked for the Ethyl Corporation in the
design of engines that would run comfortably on tetraethyllead.

Tetraethylead was invented by Thomas Midgely working for Charles Kettering
and introduced as an anti-knock additive in 1922. It never, and I repeat
NEVER was ever used nor would the engine benefit from its use as a high
temperature lubricant.

Design changes necessary for engines to scavenge tetraethyllead deposits were
the use of valve rotators, counterbored valve guides, hard-faced valves and
seat inserts, and the use of an interference angle between the valve face and
valve seat. The deposits of tetraethyllead served no useful purpose as a
lubricant with the minor, and very minor, effect they might have in
inhibiting valve seat recession but only in engines that do not use hardened
valve seats, and these are few and far between.

During World War II the Germans introduced iron carbonyl as an anti-knock
additive in their synthetic avgas. Although this material worked well to
suppress knock, the horrendous deposits of Fe2O3, (rust) limited engine life
to not much over 100 hours. For the Germans this did not matter much as their
war planes seldom lasted that long in combat anyway.

During the '50s Mercury would not warrant engines that were run on leaded
fuel and insisted that their engines be run on unleaded straight-run marine
fuel until this fuel was discontinued in the early '60s.

All our antique and classic marine engines were designed to run on the
standad unleaded 82 octane number straight-run marine fuel. There is
absolutely no need for any kind of additive whatsoever to replace
tetraethyllead in our antique and classic boat engines because it was not
there in the first place. You run the serious risk when you add a
tetraethyllead replacement (which is unneeded) that you will form combustion
chamber deposits and serious engine damage will result.

As a parting comment, there is no need to add anything to the fuels and
lubricants available on the market as they are the result of literally
billions of dollars of research and are the finest products we have had
available for engines ever.

Sincerely,

Gordon H. Millar, P. E.
Co-Editor of The Sheerline A.C.B.S.