A swing in ambient of 85F is worth about 9 psi variation, on cold tires. If they were set at the middle of that range, then you would see 4 or 5 psi overinflation in summer, and 4 or 5 psi underinflation in winter. That applies to both air and nitrogen.

May be time to invest in a new tire pressure gauge.

Nope, I have a good one. I always measured cold tire pressures and it was always right around 32 psi. Temps on average are between 30F to 90F with higher and lower being extremes. I would imagine that your temperature fluctuations are more drastic than mine. Even with regular "air" temps don't seem to affect tire pressure where I live very much. What impressed me more than anything about the nitrogen was that I never had to add any. There seemed to be no significant loss of "nitrogen" over a 3 year period. Seems like MD noticed a difference in how well it help pressure too.

I can understand it not losting pressure much over time. I haven't notice that my tires don't change with time, given that they have a new seal to the rim and new valve stems, and nitrogen could be a bit better in that regard.

I think your annual swing in ambient there is more like 30F, the same as my 15C swing. Expansion is pretty much a constant for any gas, and that amount of temperature swing will give a 3 psi variation, summer to winter.

Of course, if one parks in a garage that is a constant temperature all year, and measures the tire pressure in the garage, then you won't see the swing.

It's funny that those that fill with N2 are still checking their pressures regularly like the rest of us. I used compressed air and hardly ever have to add air. So let me summarize:

$30 to fill with Nitrogen = bend over and let the dealer nail you :stickpoke:nanana:

Sorry, needed to inject some humor.

I can understand that you may feel it is not worth paying for. I do check my pressures quite often and have an air compressor at home, so I didn't opt for Nitrogen this time either. It does have it's benefits though.

I have a turbo-n-ator which is is a device which creates entering the air intake to spin. This vortex action causes more horsepower. Proven... I will sell it for 30$.

I also have a Cold Air Intake for the new turbo motors.... 25+ hp because it used cold air. Hello Cold air has more O2 = More power.

I also have a platinum ionizer inducer which adds ionized platinum to the combustion chamber which will cause a 100% combustion in the cylinder so you get much more power and added MPG.. It is the same stuff that is in Catalytic converters which is used to burn the unburnt fuel.

I had to get up in the middle of the night to feed one of my twin boys. As I was laying in bed trying to get back to sleep I started thinking about this thread.

I don't drive my M3 in the fall/winter and consequently my tires, especially the fronts last a long time. In the past five years i've had the same front tires and I must have inflated them to correct pressures about a dozen times. If the O2 molecules diffuse out of the tire and I am reinflating with compressed air which consists of 78% N2 and 21% O2, then after this five year period my tires would now be inflated with mostly N2. And all for free :D

That is how they make Nitrogen by bleeding the smaller molecules out through a membrane. The reason you don't have pure Nitrogen is that you are still replacing the other molecules in the air when you refill with compressed air.

COSTCO has their own Nitrogen generators they don't fill from bottles so after the investment their cost is low and they do not charge for this service.

This thread is gone a bit on the ridiculous side, it is like saying what is your favorite color then arguing about it.

If you want to run Nitrogen run, if you don't then don't...simple as that.

I just know from many years of using it, way before COSTCO starting using it, my pressures only fluctuate from temperature not leakage. I live in CA and run my tires overinflated so even on a cold day here my tires are above factory recommended. BUT I STILL CHECK MY PRESSURES OFTEN because it is hard to tell inflation pressure from the look of the tire, it is just good practice.

I was just rambling...but really if O2 is difusing out and I'm replacing it with a mixture that is 78% nitrogen after many years the nitrogen content has inreased to higher level.

BTW, BSM is the best colour. No arguments! :stickpoke

Interesting comment. You are correct, that if what the nitrogen proponents say is true, then the Nitrogen concentration in the tire should increase over time and the need to provide make-up air should decline over time. It would be interesting to have someone take an air sample out of a tire when it is worn-out and being replaced to see what the Nitrogen percentage has become over the life of the tire.

Not worth it for an individual to do, but it might be an interesting test for an auto magazine to write about. If the nitrogen content really does increase, it would be a confirmation that the O2 preferentially diffuses through the tire. But if the Nitrogen content does not increase...