Assuming it's a metal tank (many are plastic now) Shops (often radiator shops) specialize in repairing gas tanks: the major cost is probably the labor in removing the tank from the car. They may repair a small leak . . . . will often boil-out the tank then coat the interior with a plastic compound to prevent future problems. In my area, $100 for the entire job but probably more in urban areas.......still cheaper than a new tank.

Another decision to make: if it's a fuel-injected engine, you probably have an electric fuel pump located inside the tank. That makes repairs more costly . . . . and you have to consider having a new pump installed while the tank is out . . . . more expense but again, removing the tank is a high-labor item so maybe you want to replace the pump while the tank is out of the car.

So you want to know how much to fix a leak on a unknown tricycle? You are kidding right? Make model year engine size where on the globe matters Where is it leaking from? Newer the car the more you pay

Good luck

Lr

If it is in a gas main supplying New York City, it may cost tens of thousands of dollars. If you car's gas tank, maybe a hundred bucks or so.

about 300