Aerodynamics won't save the day where trucks are concerned since the size and weight are still problems. Note that even 18-wheelers aren't very streamlined, and fuel costs are a severe burden in that market.

"it's doubled in the last year. this seems to prove my conspiracy theory that the oil companies and car makers are in each other's pockets."

Logic takes a steaming dump on that theory, because profits may be tracked and the car companies that weren't prepared are getting hammered. Car companies need CHEAP fuel so they can sell feature-bloated pigmobiles for high profits, which worked just fine until recently.

Here's a more logically supportable theory:
The vast majority of customers are drooling idiots who don't think more the "me want shiny object" and buy accordingly. The average person knows NOTHING about what they drive or think they want to.