1954 Packard Pacific 359 L8 / optimal oil weight

Posted by 54packpac On 2021/1/22 21:34:39

Hi Howard,

I hope all is well. I have scoured the forum in search for a straight answer on the optimal oil weight for my 1954 359 L8. To no avail. I currently use AMSOIL 10W-30 synthetic ZROD oil with a FRAM C134PL by-pass oil filter. I have also used a WIX 51080 filter. All works well. AMSOIL ZROD oil comes in 10W-30, 10W-40 and 20W-50. The car is only driven from spring to fall. The average speed +/- 40mph with some pinging north of 55mph. What are the pros/cons of using 10W-40 or 20W-50? Wouldn't 20w-50 provide optimal protection for such and old engine and high heat? Would the old oil pump be stressed with 20w-50?

Regards,
TC