If anyone wants to know here is the response from shell. I asked: Do your high mileage motor oils contain zinc and phosphorous that would be good for flat tappet engines?

They responded: If you are seeking higher zinc and phosphorous contents you may have to look to a racing oil. We have a product that is called Pennzoil Racing Motor Oil and is available in SAE 25W-50. It has approximately 1800-2000 ppm of zinc additive for extra wear protection. Other engine oils with comparable anti wear protection would include Shell Rotella T 15W-40.
The zinc and phosphorous levels were recently reduced (from the API SL levels) as there has been concern that the oil that makes its way in to the combustion zone of your engine, carrying these anti-wear metals was burning and poisoning the catalyst in the catalytic converters.
Should you desire to speak with a technical representative to discuss this issue in more detail please call Pennzoil-Quaker State Technical Information at 1-800-237-8645, option 32.


Dont know if this helps but guess I wont use Pennzoil high mileage in my jeep anymore.