Fuel Efficient Vehicles make people think that if they buy them, they will be "Environmentally Friendly". In actuality, they just look like dicks.
Some People think that buying hybrids and then putting eco-friendly vanity plates (ERTH-SAVR, GOODMPG) on them makes them clever, or funny. Reasoning that if they see how clever they are, that you can spread the cleverness around, and save the earth.
A study shows that 57% of people buy priuses "to make a statement".
That statement is that they are "non-conformist, because they are buying a mass-produced japanese car"
Some people convert their old cars to run on McDonald's Fryilator grease. This just pisses people off because it smells like hamburgers, and makes them hungry.