I want to start listing Mercedes cars as well and provide similar information. My question is.will I drop out of favour with Google about my Ford cars because they might start to think my site is now more about Mercedes rather of Ford.
My point is, is it just safer to start a seperate site? I'd prefer to provide the information about Ford and Mercedes on the same site because of customer crossover. But I wouldn't risk it if there is any chance of loosing hard won ranking on Google for Ford Cars.
The keyword examples I've given are hypothetical, but my need for reliable information in this scenario is real.