Oil is mostly formulated for emissions engines with roller cams. It may not have much zinc or other soft metals that help protect cam lobes and lifters. Most car engine builders no don't want to sell solid or hydraulic lifters without rollers due to a decades long rash of lifter and cam failures.
There are diesel formulas or additives made to help these issues. A friend ran 70wt in his alcohol dragster, they added several bottles of axle lube per barrel of oil just to get the zinc and other additives.
The above is my opinion and not intended to begin an oil discussion, only to explain what I believe may be happening. this began when the automakers went to roller cams.