Aircraft piston engine makers like Lycoming and TCM have never provided any actual evidence that unleaded avgas increases engine wear. Their assertions that leaded gas provides lubrication are anecdotal and borderline superstitious. TCM pretty much admits this in its literature:
"Field experience has determined the use of unleaded automotive gasoline to be the cause of premature cylinder replacement due primarily to rapid and severe valve seat recession." [1]
They don't ever present evidence from controlled testing that backs up their "field experience". And controlled testing of automotive engines has shown that leaded fuels don't provide any significant protection. [2]
Twenty years ago, aviation writer John Deakin issued a challenge for anyone to provide good evidence that leaded avgas prevents engine wear [3]. As far as I know that challenge was never met .
"Field experience has determined the use of unleaded automotive gasoline to be the cause of premature cylinder replacement due primarily to rapid and severe valve seat recession." [1]
They don't ever present evidence from controlled testing that backs up their "field experience". And controlled testing of automotive engines has shown that leaded fuels don't provide any significant protection. [2]
Twenty years ago, aviation writer John Deakin issued a challenge for anyone to provide good evidence that leaded avgas prevents engine wear [3]. As far as I know that challenge was never met .
1 - https://web.archive.org/web/20171004135916/https://pceonline...
2 - https://archive.epa.gov/international/air/web/pdf/vsr-finald...
3 - https://www.avweb.com/features/pelicans-perch-55lead-in-the-...