There are two gas stations at the Airport. One Esso station is at the Steigenberger airport hotel. Just follow the signs for the hotel and you will find the station. A second gas station (Shell) is at the LH base (Gate 21). The Esso Station is easier to find. If you have a navigation system just search for Steigenberger airport hotel.

The rental car return at T1 is at parking area P2/P3. Arriving from Koblenz you will probably arrive on the A3. Take the exit for Frankfurt Airport. Follow the signs to Terminal 1. At the on ramp for Terminal 1 you will see the signs for P2 / P3 and the rental car return. As soon as you are in the return area look for your rental car company signs.