Warning - This whole post is going to be a major spoiler about Cars 2.
Here's the set-up for Cars 2 - a wealthy car (all of the characters in this movie are intelligent vehicles) converts to "green", converting himself to electric power and inventing a new alternate fuel. In order to publicize the new fuel, he sponsors a set of races. The competitors will use the new fuel.
The villains, a collections of lemons like the AMC Pacer, found that the new fuel becomes explosive under special conditions. They use a modified TV camera to cause race cars to blow up, discrediting the new fuel. In the meantime, the lemons control the world's biggest unexploited oil field so they will get rich by scaring cars away from the new fuel.
Big Oil vs the Environment. And the good guys have to prove that the alternate fuel is safe. Typical liberal message-movie, right?
But wait - it turns out that there is no miracle alternate fuel. It is just regular gas with some additions to make it explosive. And the head villain is the car who sponsored the races in the first place. He never converted to electric and the whole plot was just meant to discourage research into alternate fuels.
So the car who represents alternate fuel also represents Big Oil. That really messes up the message.
Actually, the whole alternate fuel plot was nothing more than an excuse to drive the movie.