Does anyone know the MERV rating of car cabin air filters? I imagine it varies by the brand of the car. If so, which brands provide at least a MERV 11 filter or better yet a HEPA? I'm not interested in a free-standing HEPA inside the car, it will be ineffective due to the constant infiltration of new dust as well as being noisy. Yes, I'm thinking of changing my car just so I can get a cabin air filter -- the one I have now doesn't have a filter and it doesn't seem possible to retrofit one in it.