Having only 1 car, I don't have much evidence. However my family's car history went like...
1. Hyundai (a Pony! Yes!)
2. K-Car
3. Ford Taurus
4. Chev Corsica
5. F150
6. Chrysler Minivan
7. Grand Am
then the parentals left the country. Having taken large depreciation hits on a lot of those (the last two especially as they were bought new...the others were bought used so not much to depreciate), and plenty of repairs, and now that they have cash...I doubt they'll be buying domestic ever again.
Personally I think I would be more likely to be dealership loyal than brand loyal, and possibly brand disloyal, but hard to say for sure...