Packard Forum Index » V-8 (1955-56)

Hello all, I am completely tearing down and trying to clean my Patrician 352. There was a lot of sludge and dirt. Engine has around 38,000 miles and appears to be original shape. I am disassembling the hydraulic lifters and trying to get any and all old sludge or oil deposits out. I have been trying to research correct oil replacement for the straight 20W per manual. I live in central PA and car will be started from time to time in the winter to circulate fluids. I was wondering if a synthetic 5w20 would be too low of a viscosity oil to use. I am planning on changing to the Mellon oil pump as well, unless I would lose important vacuum features as the wipers or anything drastic. I am also replacing new seals and figured a synthetic would be fine then. Was thinking of Valvoline or Castrol. Thanks for anyone's input or expertise on this. I wanted to figure out what to use so I can fill the lifters before re-assembly.

I did some searching on this forum a couple years ago to determine the best oil for my 1955 Caribbean 352, and recommendation from Jack Vines at that time was to get 20w50. I ended up getting the NAPA High Mileage version of 20w50 and it's worked great so far.

Here is the original thread discussion:https://packardinfo.com/xoops/html/modules/newbb/viewtopic.php?post_id=8555

In 1956 Packard recommended 10W30 as an alternative to the 20 weight oil. 10W30, 15W40, and 20W50 are variously used. If the engine is in tolerance I would personally just use 10W30 especially because you want to run it in winter, but if the engine has significant wear then maybe up it.

I have a 55 400 and did not notice a difference in oil pressure between 10W30 and 15W40, but my engine just had valves machined and rings replaced. Supposedly about 40k miles since new in mine currently.

Thanks for your advice. I may go with the 10-30 then. Do you see any reason not to run synthetic? I figure the new seals should be ok and I cleaned out all the old sludge.