I have done a ton of research on this subject, talked to all of the Cam manufacture's as well. What I have found is the ZPPD ( zinc phosphorus) additive pack is a thing of the past, its gone and not coming back as this additive pack clogs the cat's on all modern cars. This has a very bad effect on Flat tappet Camshafts as without the ZDDP a flat tappet cams life span "CAN" be very short.
The additive pack in most if not all Diesel oils like Rotella is complettly different that what is required for a flat tappet cam. And even in those diesel oils the ZDDP has been reduced, in Rotella from a high of 1310 PPM down to 1055 PPM. Flat tappet cams require a long string high density zinc, phosphorus. Diesel oils contain ZDDP alright but it is just the opposte, it is a short string, low density additive pack. Think about it guys if you are running an after market cam, spring kit with an increased ramp angle and more spring pressure PSI reading at the cam lobe-lifter junction can reach as high as 250,000 PSI to 300,000 PSI. It takes Zinc and Phosphorus of the required type to let the cam live.
All of the cam folks I talked to said this: " Running a stock or close to stock cam, requires a ZDDP level of around 1000 PPM, maybe even as low as 900 PPM would be ok, MAYBE. if you are running a High Lift cam and springs then you need at a minimum of 1250 PPM and 1300 PPM would be even better. That leaves out a hell of a lot of the oil we have today.
The two oils I found that will meet all of these standareds are Valvoline Racing Oil, and Brad Penn Oil. There is one more that may be just as good but I hate the guy so don't like to even mention there name, that would be Joe Gibbs racing oil- Yea the Nascar guy. Interesting for these oils to be marketed they all had to print on the Label " Not For Highway Use" and all of the cans I have of Brad Penn and Valvoline racing oil do in fact have this printed on the label.
I simply spend way to much on the motors in my Hot Rods to take any chance. I have switched all but one of my motors over to Roller Cams to avoid this problem. However even in the Roller Motors I am using Brad Penn, it cost a little more granted, but just how much is protection worth?
Roland