Re: Oil Weight for 1951 288 that had rebuild 20-25 years ago

Posted by Redhexagon On 2022/9/26 0:46:41

Packard indeed recommended SAE 20 in warm weather.

SAE 10w-30 is thinner at 32*F than SAE 20, and thicker at 212*F than SAE 20.

In other words: SAE 10w-30 protects your engine better in both hot and cold than SAE 20.

It's not just for winter use, either. SAE 10w-30 is the same as SAE 20 at around 100*F. It's thinner below that, and thicker above it. That means 10w-30 will flow quicker when you start your engine on a 70*F Sunday morning.