[newnewpdro]

This is correct, but it's also been overstated how important the lubricating properties of leaded gasoline were in these engines - while the harmful health effects were understated. [1]

[1] www.walshcarlines.com/pdf/mechanicalimplications.d4e.pdf

[olivermarks]

I've found it varies by engine type. International Harvester light line SV engines for example definitely benefit from lead additives to fuel. Zinc additives in oil is another 'be kind to your engine' additive https://zddplus.com