I just reviewed the PDS for Rotella T4 15W40, and I noticed that Shell now lists this HDEO as a synthetic blend. To confirm this claim, I contacted Shell and received a response stating that the formulation for Rotella T4 15W40 was upgraded to a synthetic blend in January of this year (2021). Given the lack of industry standards or regulations defining requirements for synthetic blend oils, the percentage of synthetic base stock, probably Group III, is unknown.
I noticed that several 15W40 conventional HDEOs, including Mobil Delvac 1300 Super and some store brands, are now being marketed as synthetic blends. However, all the oil marketers are not disclosing the percentage of synthetic base stock. So, the question: do these upgraded HDEO formulations provide any real performance advantages over Group II base stock diesel oils?
I noticed that several 15W40 conventional HDEOs, including Mobil Delvac 1300 Super and some store brands, are now being marketed as synthetic blends. However, all the oil marketers are not disclosing the percentage of synthetic base stock. So, the question: do these upgraded HDEO formulations provide any real performance advantages over Group II base stock diesel oils?