"..HDEOs aren't mentioned anywhere in the article"
I didn't say that they were. When posting I stated " In addition to having more additives designed to address corrosion, HDEOs should do better for low use rates as they're thicker.", as most HDEOs being used are thicker than most PCMOs being used. Since one conclusion of the article is an impression based on observations that they had been making for awhile;
"Until now, we've always believed that to the extent multigrades might not be protecting camshafts as well as straight-weight oils, it might simply be because multigrades which are thinner at ambient temperatures than most straight-weight oils simply run off of the parts quicker in an inactive engine, leaving steel parts exposed to the elements. However, SAE 951035 suggests that even in an active, running engine, straight-weight oils protect against wear better than multigrades. (Remember, in the SAE study, actual wear rates were measured while the engine was running.)"
it seemed reasonable to assume that a thicker HDEOs would provide better corrosion protection than a thinner PCMOs. Also, if additives are being used in part to address corrosion then it's reasonable to assume that more of the additive in an HDEO will provide more protection than less of the additive in a PCMO.
