Mechanic job should be reworked first.
They are running around with unlimited amount of gas and filling cars instantly in matter of seconds... First they should have limited amount of gas, it should cost higher as they are mobile unit, their filling up should last a bit longer..
For example, player joins mechanic duty at GS. He have 0/200 liters in beginning. He first needs to buy at GS which will have lower price of gas. I understand that will mean the players will more often go to GSs which is kind of a point, but as being mobile and not a stationary unit, mechanic has its own benefits. When someone asks for mechanic and one arrives at scene, he can fill up players car like it was by now but that process should last a bit more. Like at GS, 10% per second or something like that.
Also, gas price at main GS should be highest then others so players actually looks for alternative GSs and this state owned GS needs to go to bankrupt :3