Not sure if it's been mentioned, but for those of you who are new to doing crops and frames, be careful about how close you're getting to your subject... leave some space for your subject to "breathe". I used to do this a lot.
I see a lot of pictures where the crops are within a pixel or two of (or sometimes touching/overlapping) the subject, which just makes things feel really cramped/tight. There is a time and place for everything, but for the most part, it's good to give your subject some room.
I know this isn't a car, but it's just a quick example:
400mm @ f/5.6, ISO 100: