[T3] Overrated Ethyl

["Steven Ayres" <comwest@att.net>]

This issue comes up once in a while. From what I've read, I think the
concern about exhaust valve recession with unleaded fuel, even in engines
that are clearly designed for leaded fuel (i.e., those with cheapo cast-iron
valve seats), is way overblown, to a large extent as a result of
fuel-industry marketing.

Consider this test, reported by Buick engine designer John Mitchell for the
Triumph club. Notice that seat recession indeed occurs, but after 20
consecutive hours at WOT and 4000rpm!
http://www.vtr.org/maintain/valve-seats.html

Real-world engines, particularly in old cars, rarely take this kind of
abuse. Then there's the overall cost/benefit analysis that is often
overlooked:

http://www.mindfully.org/Pesticide/Lead-History.htm#cars
...
Today the mechanical benefits of unleaded gasoline are obvious. Ever wonder
why your new car goes longer than your old one between spark-plug changes?
Or why exhaust systems last longer? Or why oil changes don't need to be as
frequent? Try unleaded fuel. In a report delivered to the Society of
Automotive Engineers, lead-free fuel was shown to significantly reduce
engine rusting, piston-ring wear and sludge and varnish deposits, as well as
to reduce camshaft wear. In 1985 an EPA report concluded that reduced lead
levels reduced piston-ring and cylinder-bore wear, preventing engine failure
and improving fuel economy. Estimated maintenance savings exceeded the
maintenance costs associated with recession of exhaust valves, which is
caused by the use of unleaded gasoline.

Gary Smith, an English Ford engineer working in the area of fuel economy and
quality/vehicle/environmental engineering, told The Nation: "The higher the
lead content, the more it messes the engine oil up, and we wanted to get
longer intervals between engine oil changes, so that's a negative for lead
as well.... [The scavengers used in leaded gasoline] or combustion of
anything with chlorine or bromine will make hydrochloric and hydrobromic
acid, so the actual muffler systems get corroded. They end up on--and
affect--the spark plugs. Because we're trying to keep warranty costs down
and [lower] costs for customers, we found ourselves going away from lead."
...

Lots of other interesting info on that site.

So running leaded fuel actually *adds* maintenance cost rather than lowering
it -- leaving aside entirely the profound impact of lead on human health and
the environment. And all because Dupont owned 35% of GM in the '20s. Sheesh.

Now it's obvious that few drivers in the developed world can even make this
choice anymore, but my point is that exhaust seat recession in some old
engines -- *not* Type 3s -- while it can happen, is a really minor concern
and hardly worth talking about. So I'll shut up now. ;)

Steven Ayres, Prescott AZ
'66 KG1600

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