And to mention the cheapest tire gauge is probably better than a SLIME air pressure gauge.To start with gas station air pumps are notoriously inaccurate.
Tire pressure should be checked and adjusted on a completely cold tire.
Why would you set your pressure to 40 instead of what the label on the drivers door post lists?
LMAO the cheap tire gauge did match the reading from the TPS
"Tire pressure should be checked cold tire." And the best way to do that, Ford Pass .