I came outside this morning and noticed a puddle underneath the back of my car (W126). I stuck my finger in it and smelled it and lo-and-behold it was diesel fuel. I looked under the back of my car and saw a small little bung or hole (looks like a drain of some sort) dripping onto the ground. I didn't jack my car up yet or anything to get a better look at it but it may be coming from in front of the tank too. Like I said, I can't tell yet but it looks to be coming out of that drain. It doesn't do it while the car is running. I'm at a loss. Any suggestions?

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1963 Ford F100 - Cummins Swap?
1985 Mercedes 300SD - 210K
1992 Ford Festiva - 92K
2001 Ninja 250 - 8K

check and see if you put the fuel cap on properly.. I didn't one week and I got diesel everywhere and it dripped from out of the trunk as well

Im almost 100% sure I have. Why would it leak if the fuel cap is loose? I mean, shouldn't the fuel system be sealed anyway and not depend on pressure generated by a gas cap to not leak?

I've also noticed a significant decrease in gas mileage, and not just from this tank but the last few. Its gotten alot worse with this one but I think I have a couple broken teeth on my gears for the odometer/trip meter.

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1963 Ford F100 - Cummins Swap?
1985 Mercedes 300SD - 210K
1992 Ford Festiva - 92K
2001 Ninja 250 - 8K

not from the fuel system but the sloshing around of fuel.

Did you know that all non metal fuel lines are supposed to be replaced with new lines ever 2-3 years? How much do you want to bet you are on the OG lines?