When I wander the pits at the NHRA fuel cars and look, it seems that the oil used by major teams is a secret. Plain jugs with a slap on sticker of their oil sponsor. Nothing ever directly poured in the oil tank from factory packaging except Red Line on a few teams. Racing is strange that way. Seeing the water and oil temperature of a NASCAR engine at Talladega with their closed off front ends in August for 500 miles in 98F temperatures leads me to believe that if there isn't any or very little Group III oil in the car. 500 miles in an engine producing from 2.4 to 200 horsepower per cubic inch is not relatable to highway miles on a passenger vehicle. Rebuild after every round in fuel cars. Refresh after every race for top Nascar team engines. Yeah, I imagine they are using PAO/POE and a dash of carrier group in their cars. Nobody can bring the evidence otherwise so it is hearsay. I do believe the pro stocks are using a pretty standard hydrocracked low viscosity oil in their cars though as evidenced by one of our board members that creates oil for some NHRA pro stock teams. Maybe he will chime in. I would like to hear if Group III has surpassed Group IV in objective testing and in which categories other than solvency.
The reason for the secrecy is the same reason they won't show the chambers of the heads, the camshaft, etc... Other teams are watching. If a team finds a combination that works well, they don't want to give that information out to other teams willingly.