Classic cars need frequent oil changes due to less efficient filtration and blow-by; modern detergents can help

https://wiki-legion.win/index.php/Full_Service_Oil_Change_Greensboro:_What_Every_Driver_Should_Know

Classic cars need frequent oil changes due to less efficient filtration and blow-by; modern detergents can help, but always choose an oil with appropriate zinc levels for flat-tappet cams.