Honest-to-goodness leaded gasoline was still available at many gas stations in Las Cruces, New Mexico in 1993. When I moved there in 1989, I thought the availabilty of leaded gas was very unusual; leaded gas stopped being sold in New York in the early 1980s IIRC.
To this day, I hear a lot of old people refer to premium gasoline as “ethel” or “high test.”
In 1987, I was told in my mechanics training that the leaded gas sold had virtually no tetraethyl lead. Leaded gas was completely phased out at the end of that year. If any pump gas in the U.S. has lead in it then it was added in violation of EPA regulations. More likely, the owner just never bothered with replacing the sticker on the pump.
Lead was added to gasoline for two reasons, to reduce detonation (i.e. to increase octane) and to protect the engines’ exhaust valves. As the exhaust valves of an engine open and close, they’re alternately heated by the exhaust gases that blow past and then pressed against the iron of the heads. The valves in older engines were made of untreated steel and the heads were iron alloy. Without tetraethyl lead, the valves would weld themselves to the head much in the same way that a blacksmith welds steel by heating it in a furnace then hammering it together. Over time this destroys the valves and seating areas.
Lead was added to gas to perform a chemical vapor deposition. The lead is vaporized during combustion, is deposited on the valves, and the softer lead creates a barrier layer that keeps the valves and head from bonding together.
Lead in pump gas was phased out for two reasons. First, lead was released into the general environment. Second, besides coating the exhaust valves the lead also coated the pellets in catalytic convertors and (in later models of cars) it coated oxygen sensors, so not only was lead sent out the tailpipe, the emissions controls in a car were destroyed.
Other additives have replaced lead as octane enhancers (I think that MTBE has been banned as well.) The exhaust valves and seats are now made out of harder materials.
Admittedly, this is a biased source, but I don’t think that they would fudge facts that were this easily refuted.
I guess I was wrong about the nozzels. But like I said, it’s been years and years and years since I’ve seen a pump for leaded gas. (I think it was phased out in the early 80’s around here.)
On a technical note, does anyone know how leaded gas ruins a catalytic converter? Does the lead react with the catalyst and spoil it, or is it more a matter of lead deposits gunking up the works? To use engineering jargon, does lead poison the catalyst or foul it?
It coats the catalyst.
teleute12,
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