Congress can hold hearings on anything. If they wanted to, they could pass a law regulating any aspect of oil companies they wanted to-- it's all "interstate commerce," which Congress can regulate.
Passing a law against high gas prices (or "excessive" profits which are just the result of the higher dollar figure in sales) would be a terrible idea that could not work, and which would be a bad idea even if it did work, but Congress has the authority to pass a lot of dumb laws. They're really good at it.
But you're right, the hearings are just grandstanding, like most of what they do. If they wanted to do something smart about transportation policy they'd be looking to fix our railroads.
By the way, did you know that the Honda Super Cub motorcycle gets around 350 mpg? And didn't Back to the Future promise us a Mr. Fusion?