Pennzoil and Quaker State are both made by Shell, who acquired the companies about 10-15 years ago. Just branding.

Shell is one of the world's largest lubricant manufacturers and makes oil for the Ferrari Formula 1 team and Penske's INDYCAR and NASCAR teams. They have a custom fuels and lubriants lab just for racing.

The oils from 10-15 years ago are very different than today and today's are much better.