Miss Z, most gas station air compressors have a gauge directly on the nozzle. when you push it in to fill, the gauge readout will pop back that tells you how much psi is in your tire. You can compare what it reads to what your car reads.
Also, filling air IS NOT like pumping gas, it won't automatically stop. Just push it in for 5 seconds and see what the guage reads. Then kung kulang pa, put it in for 5 seconds again...repeat if necessary.
At least that's how it worked with the last virgin I had...este car pala.
