It's getting cool out - check those tire pressures!
This morning I was greeted by the TPMS light on the dash.
Went right to the gas station and got them back up to summer pressure.
Remember every 10 degrees is 1 psi.
So if your tires were at 40psi in the 100 degree summer, they will be 34psi on a chilly 40 degree morning.
I think my dealer had dialed down my pressures to the low 30's.
I'm kicking myself for not checking them.
- Kris
Went right to the gas station and got them back up to summer pressure.
Remember every 10 degrees is 1 psi.
So if your tires were at 40psi in the 100 degree summer, they will be 34psi on a chilly 40 degree morning.
I think my dealer had dialed down my pressures to the low 30's.
I'm kicking myself for not checking them.

- Kris
This morning I was greeted by the TPMS light on the dash.
Went right to the gas station and got them back up to summer pressure.
Remember every 10 degrees is 1 psi.
So if your tires were at 40psi in the 100 degree summer, they will be 34psi on a chilly 40 degree morning.
I think my dealer had dialed down my pressures to the low 30's.
I'm kicking myself for not checking them.
- Kris
Went right to the gas station and got them back up to summer pressure.
Remember every 10 degrees is 1 psi.
So if your tires were at 40psi in the 100 degree summer, they will be 34psi on a chilly 40 degree morning.
I think my dealer had dialed down my pressures to the low 30's.
I'm kicking myself for not checking them.

- Kris
Also, when I filled them the light was still on, even tho it was about 70. I took the pressure and all 4 wheels were @ 26.5 psi. That really pisses me of cuz I had gotten an oil change 2 days before. I called a cussed out the service manager and got 6 free oil changes.
But now that I filled the tires up to 40 psi, I do notice improved mpg!
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wow. never knew that. good to know!!
Joined: Jul 2008
Posts: 1,316
From: Chicago, IL
This is true, though Nitrogen doesn't expand/contract as much as air does at the same temperatures.
Just here to spread some news on nitrogen...
First of all, there is nitrogen in the regular air that you typically put in tires. It can be as much as 75%.
The nitrogen molecules are larger than that of air therefore the theory is they diffuse through the tire at a rate less than that of compressed air. So, by putting nitrogen in your tires you are removing moisture in the tire and reduce the rate at which these molecules escape the tire which theoretically maintains pressure more steadily and over a longer period of time.
One thing I don't know for sure is if nitrogen is lighter than compressed air. If it is this could be a potential benefit. Any unsprung weight that you can shed is always a good thing.
One thing I do know is that nitrogen does not support combustion and therefor will not start a fire in your tire.
First of all, there is nitrogen in the regular air that you typically put in tires. It can be as much as 75%.
The nitrogen molecules are larger than that of air therefore the theory is they diffuse through the tire at a rate less than that of compressed air. So, by putting nitrogen in your tires you are removing moisture in the tire and reduce the rate at which these molecules escape the tire which theoretically maintains pressure more steadily and over a longer period of time.
One thing I don't know for sure is if nitrogen is lighter than compressed air. If it is this could be a potential benefit. Any unsprung weight that you can shed is always a good thing.
One thing I do know is that nitrogen does not support combustion and therefor will not start a fire in your tire.
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