atalarico
Senior Member
The fluid is just water condensation mixing up with a little bit of black soot. Perfectly normal catalytic converter function, it converts Carbon Monoxide, hydrocarbons and other nasty gases into harmless water vapor. All exhausts with a cat will do that.
I did not notice any MPG gains with switching my muffler (I had on previous toyotas) so there's no gains to be had. Only switch if you need to or want a more "sporty" sound to it.
Good to know! It just seemed like it's been more condensation in the past couple years than before, but I dunno. Science!