since nascar engines have 5 gallons of oil and 4 seperate feed lines from the oil pump i would bet the wix filter if used is probably hollow . no need to filter just get max flow for the short time they are run, back in the 1960s i knew some of there tricks but nothing about any special oil mixtures
johnny dont know your age but back in the 60s i got to be in the pits with richard pettys crew at mich. also sepnt time in drivers meetings and got to know some of there tricks, the on i remember most was when petty ran a ford which had coil springs and during his first pit stop a wooden block fell out of the left front spring and i picked it up before a official saw it, back then they only had one offical per team. the wooden block was designed to break during the race to lower the car,
i guess i will add more, in the mich drivers meeting the nascar offical was telling the drivers whoever ran over a air hose would be penalized one lap and boobby issac told him to his face if he stood in front of his car to hold him he would just run right over him and put him 6 ft under. also wendell scott , a driver some folks would not know in the drivers meeting he sat on the floor instead of on the couches with the rest, but back then they were all good ol boys.
its probably good tony stewart no longer drives for joe gibbs as joe would of been in his s---t tony was at goodyear and toured the production of the tires being built, a friend said he never said one word to nay of the folks working , i guess since he is now a owner he can be a jerk .. i used to be a stewart fan