There's been ways of improving MPG with cars for decades, just that most of those patents belong to oil corporations in one way or another. They won't make money, sad isn't it? Maybe one day we will not be so selfish, although some say it's human nature.
I honestly can't see thorium cars being widespread within the next hundred years because it's so efficient. You won't be able to keep selling it after the car has been sold like you can with gasoline or even electricity. To look at it any other way is just wishful thinking.