4 ms·

> TEL also acts as a natural lubricant of its own, the lead acting as lubricant, particularly on valve and other top end engine components. This is a myth. TE

> TEL also acts as a natural lubricant of its own, the lead acting as lubricant, particularly on valve and other top end engine components. This is a myth. TEL has no lubricative properties in engines. The reality is opposite; lead deposits are corrosive. From https://www.shell.com/business-customers/aviation/aeroshell/knowledge-centre/technical-talk/techart-18-30071600.html https://www.shell.com/business-customers/aviation/aeroshell/...: "The temperature for Lead deposits to form tend to be favourable around the spark plugs (as the whole mixture is quite cool before the flame starts to propagate) and on the exhaust valve stem (as the mixture cools after combustion). The problem is that the deposits are electrically conductive, which shorts out the spark plug - and corrosive, which can start to attack the metal of the valve stems."

Aloha 5y ago
TEL before combustion does have lubricative qualities, much in the way phosphorus does in oil or sulfur does in diesel fuel. After combustion, its like any heavy metal being burned, it turns into an oxide, which has a variety of characteristics.
- nate_meurer 5y ago
  It's the supposed benefits of the post-combustion lead oxide deposits that defenders of leaded gas cite. I have never heard anyone cite the lubricity of TEL itself. The most popular theory is that the lead oxide fouling reduces the occurence or effects of micro-welds between valve and seat surfaces, which otherwise produce abrasive particles that contribute to valve seat recession. While this theory is plausible, it has not been shown to occur under normal operating conditions in automotive engines, nor in aviation engines as far as I know. The final report from the EPA's Valve Seat Recession Working Group found no evidence that leaded gas reduces engine wear under any but the most extreme operating conditions: https://archive.epa.gov/international/air/web/pdf/vsr-finaldraft.pdf https://archive.epa.gov/international/air/web/pdf/vsr-finald... "In real world conditions, virtually no evidence of excessive valve wear has been found in vehicle or engine operation in normal everyday use, and several studies that monitored vehicles in actual daily service in countries that eliminated lead found no excessive valve wear."

Aloha 5y ago

TEL before combustion does have lubricative qualities, much in the way phosphorus does in oil or sulfur does in diesel fuel. After combustion, its like any heavy metal being burned, it turns into an oxide, which has a variety of characteristics.

nate_meurer 5y ago
It's the supposed benefits of the post-combustion lead oxide deposits that defenders of leaded gas cite. I have never heard anyone cite the lubricity of TEL itself. The most popular theory is that the lead oxide fouling reduces the occurence or effects of micro-welds between valve and seat surfaces, which otherwise produce abrasive particles that contribute to valve seat recession. While this theory is plausible, it has not been shown to occur under normal operating conditions in automotive engines, nor in aviation engines as far as I know. The final report from the EPA's Valve Seat Recession Working Group found no evidence that leaded gas reduces engine wear under any but the most extreme operating conditions: https://archive.epa.gov/international/air/web/pdf/vsr-finaldraft.pdf https://archive.epa.gov/international/air/web/pdf/vsr-finald... "In real world conditions, virtually no evidence of excessive valve wear has been found in vehicle or engine operation in normal everyday use, and several studies that monitored vehicles in actual daily service in countries that eliminated lead found no excessive valve wear."