Based on
this 2010 study, global population is expected to increase by 1.4 billion by 2030. That's like the world now minus 20 years of natural resources plus one more China.
Projected increase of just the top ten most populous countries is 676MM. The top ten countries are India, China US, Indonesia, Nigeria, Pakistan, Brazil, Bangladesh, Russia, and Mexico. They're not driving hybrids in Bangladesh. How much is a Prius? $25K? The combined GDP per capita of India, Indonesia, Nigeria, Pakistan, and Bangladesh is just under $15K.
8 of the 10 are perceived to be going through periods of industrialization where more resources are needed to fuel growth. The trucks being used to haul shit to some construction site at the next Nigerian megapolis have more impact on the global market than do the F150s that middle American douchebags use to haul their pretend boats to the pretend lake.
If every middle American soccer mom goes to a Toyota dealership this afternoon to trade in their gas guzzling SUV for a Prius, there's a small chance it would cause the price of a barrel to go down by a few pennies, but the 'impact' on oil prices would be short lasting because the global market is more defined with the actions of one billion industrializing chinamen.