"In a state as large as Texas, driving from a rural county edge to the central courthouse can take an hour. With those distances, you would expect a robust mileage reimbursement program. Prepare for disappointment."
Unlike California or federal courts, the state of Texas does not have a statutory requirement to reimburse jurors for mileage. The Texas state legislature sets the daily pay ($20 for day one, $58 thereafter), but it leaves travel expenses entirely up to the individual counties.
Because there is no state mandate, whether you get paid for gas depends entirely on which of the 254 Texas counties summoned you:
While gas isn't covered, almost all major Texas courts provide validated, free parking in a designated county garage. The golden rule in Texas is to read the back of your summons—if it says 'Park in the Red Garage,' do exactly that, or you'll be paying out of pocket.
Texas state law does not require mileage reimbursement, and the vast majority of Texas counties will not pay you for the gas used to drive to the courthouse.