Nitrogen
 

Had tires filled with Nitrogen at dealer $30 total (w/ year of refill). Running stock size sport rubber- Mich Pilot Super Sports.
Prior track days dropped presure to 30 psi before 1st session- would typically get to 40 psi after tracking- by second session if I didn't lower would get to 45 psi. (delta 10-15 psi) Basically drfting at that point - very little traction at 45 psi. Did not want to lower as low as 25 to try to keep 35-40 hot.
Gave Nitrogen a try at NJMP- was 90 F and sunny hot track this past weekend 370Z NJMP Thunderbolt Hot Laps.mpg - YouTube Started day at 35 psi - after first session only went up 5 psi to 40psi- i lowered after first session back to 35 psi warm - did not adjust after that for two days on track- despite being very hot on track only ran ~ 38 psi hot after other session.