B.M.
If you really need to learn in your car, Pimsleur is probably the best. However, I would recommend that you consider the Rosetta Stone program. These are CD-ROM's that use pictures, voice and writing to help you intuitively integrate language concepts. In other words, you learn the words the way you learned your first language.
I tried a variety of methods to learn Russian, including spending time among native speakers, listening to tapes in the car and hiring a tutor. However, the words and phrases I learned through Rosetta Stone are the ones I learned best.