Shell recommends Rotella because they don't offer a product in North America whose primary application is gasoline OHV flat tappet engines. The last one they had was Quaker State Defy 10W-40. Because it was a xxW-40, it was allowed to have the higher level of ZDDP and still carry the API SN rating. The xxW-30 and lighter oils had the ZDDP limit. That product was discontinued a few years ago. Rotella will work, but it is a compromise and there are better choices at around the same price point. Mobil1 FS 0W-40 is widely available, priced very competitively and has 1100 ppm of ZDDP.
Shell owns Pennzoil. DA Lubes of Indiana owns Penn Grade. That used to be Brad Penn, made in Bradford PA at the old Kendall facility. It may still be made there, but I don't know.
