HORRID FACT & BUTTERFLY FACT.
Every ten litres of petroleum fuel burnt in an ICV (internal-combustion) vehicle produces one kilogram of pollutants--which wreak havoc on the planet for years, or decades, or centuries, or millenia (different pollutants last for different lengths of time: carbon-dioxide averages a century). Happy motoring!
(In non-metrics the ratio is a pound of pollutants from each gallon of fuel.)
For a complete change of subject, moving from the nasty to the wonderful (and humbling), ponder this page.