I also for years used whatever discount oil I could get, the service rating is more important than just the brand.
However, the fact remains that alot of the heavy metals that once protected the flat tappet cams are not in these oils any longer.
Next time you look at new oil, look at the service rating donut on the bottle, you will see the words "Energy Conserving" . In a nut shell those oils do not have the Zink, ZDDP, need to protect the flat tappet cam's.
I have been using the Shell Rotelle T 15W 40, and it also has taken a hit from the EPA. But from my reading too, it still has enough ZDDP. But keep an eye on it, because it may change it the future.
For me I will be switching to a race oil like Valvoline. That stated right on the lable "Contains increased amounts of zinc for extra engine protection"
Here is a recent thread on this too.
https://www.yenko.net/ubbthreads/show...0/fpart/1/vc/1
Mike