[samtho]

The “couple of cents” seemed like an off the cuff remark to indicate that leaded gas was less expensive than alternatives, but I would be interested in hearing about this delta as a percent rather than a fixed cost. Given inflation, gas price fluctuations, and the sheer volume in which fuel was sold, measuring it as a “couple of cents” is completely meaningless.

[jabl]

It's hard to have any conclusive number on this, it's not only about inflation etc. but also the cost of alternative ways of achieving the required octane (e.g. increasing production of reformate or alkylate, or the refinery buying external blendstocks like ethanol or MTBE), which varies a lot over time (due to technical advancements) and place (what kind of equipment does a refinery have installed), etc.

From a 1998 article (https://www.ifc.org/wps/wcm/connect/d3706d00-3d97-495d-8b8c-.... ) it estimates between $0.01-$0.03/liter for lead removal. US gasoline prices in 1990-2000 were at around $1.20/gallon which works out to about $0.32/liter. Taking the middle value of $0.02/liter for lead removal that would be around 6%. Just as a back-of-the-envelope calculation. I think in reality in many places that cost delta at pump the is lower since the usage of ethanol as an octane enhancer shifts the cost to various agricultural subsidy programs.

[vitus]

Wapo article from 1984 [0] asserts that 85-octane nonleaded gasoline was consistently about 2 cents cheaper to make than 87-octane leaded gasoline.

That said, that was with numerous advancements over the preceding 60 years which most likely would never have happened if we hadn't developed engines capable of taking advantage of high-octane fuels.

[0] https://www.washingtonpost.com/archive/business/1984/04/01/c...

"But, as DeMuth noted, the EPA study is concerned about total costs and benefits to society, not just to one group. The study makes no attempt to predict what would happen to prices at the pump. It points out instead that the cost of manufacturing 87-octane unleaded gasoline, according to market prices, is consistently less than 2 cents a gallon more than for making 89-octane leaded gasoline. Average pump prices are about 7 cents more, however."

I believe this is the EPA study: https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=9100YK16.TXT (I clicked the "download as pdf" adobe acrobat icon on the right)

"The DOE model estimates that at current lead levels (1.10 gplg) the marginal manufacturing cost differential between unleaded and leaded regular grades of gasoline is less than two cents per gallon. Retail prices, however, diverge by an average of about seven cents per gallon (Weekly Petroleum Status Report, 1984, various issues)."

7 cents per gallon is right around that 2 cents per liter that you cite, naturally.

[vitus]

A gallon of gasoline back in 1930 (or 1925 for that matter, pre-depression) cost about 20 cents. So, even 2 cents per gallon would be a 10% savings.

https://pubs.acs.org/doi/10.1021/om030621b has some points of comparison (as well as a lot more historical context of the research that led Midgley & co to leaded gasoline if you're interested).

For what it's worth, per Table 1, ethanol is not anywhere near as effective as tetraethyllead -- it has an effectiveness of 0.1 per mol, vs TEL having a value of 118. Even when normalizing by molar mass (since TEL is a much heavier compound), TEL is still ~100x more effective than ethanol.

"... iodine had a few slight drawbacks. It added over a dollar to the cost of a gallon of fuel and we were afraid that would be considered a trifle excessive by most motorists."

"Further studies with more dilute solutions showed that a one-fortieth of one percent solution of tetraethyllead was equivalent in knock inhibition to 1.3% aniline in kerosene."

"The first public sale of Ethyl gasoline (the name given it by Kettering) occurred on February 1, 1923 in Dayton, OH at 25 cents per gallon (regular gas cost 21 cents per gallon) (Figure 8) before large-scale production had started."