FWIW - I have had personal experience with this oil.
Two years ago I bought 8 quarts of the DG brand oil in 10w30, and used it in my 1951 GMC truck, with an inline 270ci six cylinder engine. (This was spring of 2014)
I have to admit...even though it is an older engine that was rebuilt about 10 years ago, this oil made it seem to run pretty [censored]. [censored] as in there was alot of scraping noises, high engine whine, and more than usual oil dripping onto the pan in the garage.
So I dumped that oil after about 1 month. It was solid black, and seemed alot thinner than when I put it in.
Never again. I switched back to Rotella and Valvoline oil, in 15w40. No issues since.
GL