Can my landlord have my car towed from complex for being dirty (dusty)?

I live in Arizona and got a notice that I am not allowed to have a dirty car and could be towed at owner's expense. My car is in good condition and I do drive it. It does not have any flat tires and it has plates with current registation tags. After carefully examining my rental agreement, I see nothing in it that says I must keep my car clean or it will be towed.