Not sure if it's a rear axle leak or a gas leak.

Might be the recent rain and short trips I've been making and not properly heating up my engine or accelerating too much.

Please help and if it's worth to take into mechanic if it's only happened once?

It's a manual transmission car at 47,000km.

 

 

No smell! LOL haven't had time to smell but it no oil smell for sure.

 

You sure it's not just condensation in the exhaust?

 

Probably just the short trips have built up the dirty liquid there in the exhaust. don-ohio

 

Just condensation. You know that steam you see in the mornings? Some of that is hitting the cooler pipes and turning back into water. BUT, if it is dripping there you do have a hole/leak in the exhaust somewhere. I don't think that much water can accumulate in the pipe where the muffler connects. My suspicion is the bottom corner of your muffler where water can gather and sit.

 

Some pipes actually have weep holes for letting that water out. My Lincoln LS has them,but I haven't noticed whether the Mustang has them or not. don-ohio