Cars in Beach Buggy Racing 2 upgrade automatically. Each time you level up, the speeds and stats of all the cars increase. When you're Level 5, the cars are a lot faster than they were when you were Level 1.
Every car in Beach Buggy Racing 2 is balanced to be a fair match for the other cars at your current level, but each car has its strengths and weaknesses. Experiment to find the right match for your character and your Powerup deck!