Okay, I've looked on here and seen some topics close to what I want to know but I would like a more specific answer. I've only had my Z about a month and the temperature here has dropped a lot in the last week. My tire pressure warning light came on when I was leaving work the other night so I pulled into the truck stop (less than a quarter mile away), bought a tire gauge (a cheapie, it's all they had) and aired my tires up to 35 PSI. (Checked with the manual and dash) It was around 40 degrees F at the time. Was that close enough to checking them when they're "cold"?
The last few days the temp has ranged between 65ish during the day and 35 at night and my tire pressures have read between 31psi and 39 psi according to the dash gauge. And no, I don't mean on different tires, they all match within 1psi, had them all at 35 after I aired them up. I understand that there will be some variation depending on time of day, how far I have driven and at what speed, but is this with accepted limits?
And I read in another thread that the dash gauge is accurate within one PSI, is this true? Thanks in advance for any help.

 

Yes, the TPMS specs state that they are accurate to ±1 psi.

It's normal to see some wide variations in pressure as the ambient air temp changes and as you drive the car and the tires heat up. I could start at 35 PSI and drive for an hour or two on the interstate and the pressure would be up around 41psi. I've also checked the pressure in the afternoon at 35psi and see it as low as 32 the next morning because it's cooler. That's one reason why it's a good idea to check your pressure every week or two so that you stay close to the recommended pressure.

 

Check tire pressure in the morning before driving the car. 35 PSI. No need to worry about anything else.

 

Thanks for your help. Just wanted to make sure I didn't do any damage.