Is Delvac going to be better for my engine(87 300SDL with about 190k on it and a few slight leaks) in the winter with temps in the 20's and 30's over shell Rotella?

When i say Rotella i dont mean the blue bottle synthetic, i mean the cheap white bottle.

Is Delvac Synthetic?

The Delvac i'm referring to is Delvac 1300.