I just ad air as nitrogen is too hard to find & them usually charge extra....
On the lighter side our car dealer made us buy nitro fill LOL was supposed to get us better mileage & the tires were supposed to last longer (Did it while the car was under the warranty ....... Well we got 32K out of the nitrogen filled tires & so far 52 K out of the air filled tires same gas mileage...........
Personally I feel it is more of a gimmick...... unless it is in extreme conditions (200MPH etc.)