No it's because I have cheap *** china rims and they look good but are heavier than stock rims but the nitro is lighter than air ,also what does the race track got to do with it ,you think going fast in a circle give you better gas mileage, it's just a weekend car sometimes weekday car, I drive a work truck during the week, Also only race track I go to has no cars just four legs.

I totally agree MrBooby. Unless racing, nitrogen in tires makes for constant conversation about people and their money and how fast they're separated, that's about it. It's right up there with paying to get the winter air in their tires changed to summer air. Heck, I get 19-20 mpg in town and close 26+ mpg highway in my 96 es300 on my stock size 15" tires still running "air" from last spring.

The fact that nitrogen is lighter than air is not going to have any effect on your car's gas mileage. That's a common misconception. The gas in your tires only changes the weight of the wheel, not the mass. And the mass of the wheels is what's important. Those "heavy rims" shouldn't decrease your gas mileage by that much. What is your driving like, percentage wise? I do about 80% highway, 20% rural. You also mentioned that you rarely drive it, do you let the engine warm up to normal operating temperature or is it mostly for short trips (under 10 miles)? And how well do you take care of the fluids and normal wear-n-tear items?

By race track, I meant that constant tire pressure is only important to people who want consistent numbers from their cars. And that's why you would want nitrogen in your tires when racing, so that you could cancel out any variances from the air pressure. I didn't mean that it gives them better gas mileage.

On the road though, it's not that big of a deal, even if you check them once a month.

The actual atomic weight difference between nitrogen and oxygen is very close, plus the weight of the gas is basically zero compared to the wheel/tire itself. Silly to even think about it.

It's neglectable that it's more like marketing thing, unless you're using it more for a competition purposes. If you did a blind test, would not notice a difference.