As to - does a couple of psi making a difference. Yes It Does!
Our Jeep tire warning lite went on. Max psi is supposed to be 35. So I get them all to 34psi with my cheepo gauges.
Lite still on. Hours of reading the www. Trying to find physically sone non existent reset button. Owners manual nada.
My wife goes to the gas station and brings each tire to 35.
Light goes out .
An accurate gauge for an accurate life!
Inflation belongs in your tires.
Not in your grocery bill.