Whatever happened to leaded gasoline?

Back in the day, leaded fuel was as common as 15-cent hamburgers. Today, though, things are different. 

Why Lead in the First Place?

Tetraethyllead has been added to gasoline for nearly a century. “It’s a very cheap and effective octane booster,” explains Zachary Santner, technical specialist at Sunoco Race Fuels. Just 6 milliliters of tetraethyllead, less than 0.2 percent by volume, makes the difference between the 120- and 100-octane reference fuels used for octane testing, he continues.

Why Did Leaded Fuels Go Away?

To meet the emissions standards introduced in the 1970s, car manufacturers began installing catalytic converters. Lead oxide, a byproduct of combustion, leaves a residue inside catalytic converters, rendering them useless. Lead as a fuel additive quickly fell from favor.

What Happened Next?

Less lead in pump gas resulted in lower octane ratings. As a response, engines were detuned. Remember the glorious muscle cars of the ’60s and early ’70s? That all ended around 1973.

Why Is Lead Used Today in Race Fuels?

The science hasn’t changed: Lead remains an inexpensive, reliable, effective way to add octane to a fuel. Sunoco, for example, still relies on lead to boost octane above 105. These race-only leaded fuels can’t be used with oxygen sensors or catalytic converters, of course.

What About Alcohol?

Fuels containing a high percentage of alcohol–think methanol–will, like high-octane fuels, also fight knock. However, these fuels require increased fuel flow, which requires specialized equipment. Quick side note here: The lab tests done to determine a fuel’s octane rating can’t accurately score highly oxygenated fuels. “We developed this scale for measuring gasoline,” Santner explains, “and now we’re trying to use this scale to measure fuels that aren’t like gasoline–E85, for example. Finding consistent information on octane of highly oxygenated fuels is very difficult.”

Anything New on the Horizon?

Look for a new wave of unleaded, high-octane fuels. Santner says that Sunoco is about to add another high-octane unleaded formula called Evo 10 to its lineup. It’s 10 percent oxygen by weight and carries an octane rating of 105 (R+M)/2. 

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Coupefan Reader
8/3/22 12:09 p.m.

Why did leaded fuel go away and you didn't even touch on the largest issue, health of people?  A chem 101 student can tell you how toxic lead is.  And if you want to research an interesting and important historical-medical-social aspect of lead being removed from society, look at the bloody strong statistical correlation of the reduction in violent crimes pacing the reduction of lead in the environment.  It's unmistakable what the side effects were.  Only the Roman's use of lead pipes and the enduring bad decision making that the neurological effects created can possibly best our modern experiment in widespread lead use.  

03Panther UberDork
8/3/22 9:53 p.m.

In reply to Coupefan :

After reading your post on what was left out (and you are 100% correct, although I'm sure sonoco doesn't like talking about it) I tried to read whole article, see what else they missed! But my connection is too slow...

One thing that got misunderstood at the changeover time, that got wives tales started:

The lead in gasoline at the time, helped "work harden" the seat surface. So seats were simply cut into the cast head, in many cases. With the at the time important break in period, the seat would harden from use, and all was fine. Switch to unleaded afterwards and normal daily driving was still fine. But recut a stock seating area (remember, we are talking about not adding hardened inserts here), for a stock valve job most guys been doing all along, break it in on unleaded, and the valve could beat it way through the head in several K miles! Due to the seat never getting the chance to work harden. But unleaded took the blame for not "protecting" the valve. 

Dp1320 New Reader
7/17/23 10:24 p.m.

In reply to 03Panther :

I would disagree after seeing a number of older engines that ran fine with leaded fuel for years soon have problems with valve seat regression after unleaded fuels were introduced. 

Appleseed MegaDork
7/17/23 11:39 p.m.

Where did it go? To the airport.

ToManyProjects Reader
7/18/23 12:13 a.m.

Tetra-ethyl lead is an organic lead compound. Lead, when pure is relatively safe to be around. Even lead pipes aren't the worst thing ever. The issue with tetra-ethyl lead (and lead acetate, I'll get there in a minute) is that being an organic lead compound, the human body absorbs it readily, allowing the lead to do nasty things in the various systems of the body without the person going through great effort to ingest it. With the tetra-ethyl lead, it was literally in the air everyone was breathing.

The romans were boiling must (like grape juice) in lead pots to make a sweetener that was used in all kinds of stuff. The acetic acid in the grapes dissolves the lead making lead acetate, or "lead sugar" and acted as a sweetener and preservative. It was often used to sweeten wine. It's also soluble in water, and unsurprisingly, the human blood stream. surprisingly it's only been fairly recent that lead acetate has been banned as an additive in cosmetics in the US and Europe.

Lead in pure form isn't particularly soluble, and mostly presents a risk from handling because the soft lead and lead oxide can rub off on the hands and be transferred to things being consumed, with the stomach's acids doing the work of making the lead into an absorbable organic compound. But as a general rule, handling lead is safe as long as you wash hands thoroughly afterward. I always try to wear gloves when handling lead, and wash thoroughly as well.

8/26/23 8:47 p.m.

Ya- Cm, you ned to update this article. Lead is incredibly toxic. Recent recommendations from the EPA (maybe FDA) basically have said that there is no such thing as a 'safe level' of lead. Granted, they are being cautious and conservative, based on the latest research.

My father (approaching 70) is a gealogist and a certified water supply manager (I might be getting this title wrong) and recent lead tests indicated he had twice the lead load as I did, despite living the in same family home for 30+ years. He attributed it to residual lead levels he probably absorbed prior to the leaded gas ban. It sticks around, it doesn't go away, and there aren't really good options for removal after you've been exposed.

Update the article- its rather deceptive. 


MGfanatic New Reader
2/5/24 1:30 p.m.

I'm more interested in "where did ethanol free gas go?" For me it's over 25 miles to the nearest ethanol free pump. 

David S. Wallens
David S. Wallens Editorial Director
2/9/24 10:28 a.m.

In reply to MGfanatic :

See if this site helps: pure-gas.org tracks ethanol-free gasoline. 

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