I play the game on my ipad. Earlier it used to show ads only after a race to multiply the credits which was fine but now it shows ads even when we are switching modes, this is annoying. For 1 races of 1-2 minutes i have to see ads of 2-3 minutes. And the credits you get are also very less even after multipliers. You can either buy cars of new class for career or upgrade your previous ones for gauntlet. But it takes a lot of time