I get mileage reimbursement listed separately on my paystub - is this non taxable in PA or federally?

[Opus 17]

You must ask your employer.

Your employer is allowed (but not required) to reimburse your mileage tax-free under an accountable plan.  An accountable plan means you have to prove to the company the dates, business purpose of the trips, and the milage involved, usually with an app or a paper log book.  

If they pay mileage under a non-accountable plan, where you are not required to provide proof or reconcile your payments against actual mileage, then it must be included as taxable wages.