I discovered another gas station near Kavala which is even closer to the main road Egnatio than the one we wrote about earlier. It is a Shell station at the exit of the place Polistilo, about 7 km far from the highway Egnatio on the left side of the road Kavala- Drama. The trouble is that you come from Kavala on the right side track but the station is on your left side and between them is a full line. You should continue a bit further and then turn to a lay by, then carefully drive into a left side track and return to the station. 

The price on 11. 08.2011 was 0,825€

You can get more information on: http://www.gasprice.gr/main/showgasstation.asp?stationid=4609&histloc=1