It's probably not gas/fuel. It's probably water. Let's cover a few things. Combustion has a few by-products. One of them is oddly.... water. There's very little chance of a fuel injected vehicle letting out raw fuel. First off, the fuel, if present will be in vapor form. You wouldn't be able to see it. I'm guessing by your description that you can see it, and that it is liquid, as you're saying it's leaking. The water (as I suspect what is leaking) will also not be visible after the vehicle warms up. Water is still present as a product of combustion, but since the engine is hot, the water exits the tailpipe as vapor/steam. The steam, is also not very dense so you wouldn't be able to see it. You can confirm the steam by placing your hand in the path of the exhaust for a brief period, and your hands will be able to sense the moisture. Let me know what you discover.