If you're driving a late model car or truck, chances are that the vehicle is mostly computers on wheels, collecting and wirelessly transmitting vast quantities of data to the car manufacturer not just on vehicle performance but personal information, too, such as your weight, the restaurants you visit, your music tastes and places you go.

A car can generate about 25 gigabytes of data every hour and as much as 4,000 gigabytes a day, according to some estimates. The data trove in the hands of car makers could be worth as much as $750 billion by 2030, the consulting firm McKinsey has estimated. But consumer groups, aftermarket repair shops and privacy advocates say the data belongs to the car's owners and the information should be subject to data privacy laws.

Yet Congress has yet to pass comprehensive federal data privacy legislation. And although Sen. Roger Wicker of Mississippi, chairman of the Senate Committee on Commerce, Science, and Transportation, has said he would like to see federal privacy legislation passed by the end of the year, it is unclear if that goal can be met.