The survey found that if gas were to shoot to over $4 a gallon again, 40 percent of car shoppers would "consider purchasing a new fuel-efficient car right away." About the same amount, 41 percent, said that $4 gas would make them choose a "more efficient car the next time they were ready to buy a car." Even at $3.75, 29 percent of car shoppers thought buying a more efficient car "right away" was the right move. Takeaway point: when gas prices go up, people will want to have greener cars. The question is what kinds of vehicles will be available then the inevitable happens.