For every gallon of fuel burned, Gasoline, Diesel, or Jet Fuel there is ~one gallon of synthetic water produced. Propane and Natural Gas also produce water, just a little less. That is why when it is cold outside, the synthetic water looks like steam coming out the tail pipe. With a Diesel the soot mixes in with the steam and drips black oily looking slop, this is normal. Don't worry about it, the trees, grass, other plants, and bacteria will use it up to grow.
Now if you want to make a Hippie spit out his/her Starbucks, tell them their Starbucks is contaminated with Synthetic Di-Hydrogen Monoxide (H2O--Water)
Non Hippies will not care and say so what and drink their coffee, Acid Head Hippies will try to create new environmental regulations until the Chemists, Engineers, and Physicists laugh them out of the room, because even they get it.