The car wash cleans the outside of the windshield, and the defroster blows away fog from inside the cabin, but neither of these combat that streaky haze on the inside of the windshield.

A) What is it? B) What causes it?  And, C) What fixes it?

Short answers: A) Oily residue. B) Chemicals wafting off plastics, vinyls, carpets and polymers inside the your vehicle. C) Glass cleaner and an application of defogger.

“Repellent products are easy to use and can be applied quickly. I apply them every time my car goes in for an oil change,” said Ron Fausnight, group technical manager at Rain-X.

Defogger applied to a clean windshield makes it harder for fog to adhere.

Untreated, film accumulates on the windshield’s interior and reduces visibility, especially when driving towards light.

Blame those pieces of plastic inside your vehicle for the film on your windows. And that celebrated new car aroma comes from chemicals that create haze, too.

Fausnight had some advice for cleaning and treating the inside of your windshield:

-Use a glass cleaner designed specifically for automobile glass. They help prevent streaks that can lead to glare.

-Clean interior and exterior glass surfaces thoroughly before applying window treatment products. Interior glass surfaces often accumulate an oily residue that diminishes the effectiveness of anti-fog treatment.

-Use anti-rain products for exterior glass surfaces only. Interior requires an anti-fog product that can dissipate moisture and help it evaporate.

-Apply window treatment products with a terry cloth or microfiber towel. Spray the towel rather than the surface and wipe it evenly across the glass. Remove excess fluid with a clean, dry cloth to eliminate haze.

-Use the climate control system to help reduce moisture, especially in climates with high humidity. The system will help the anti-fogging solution clear glass surfaces faster.

-Avoid getting window treatment products on rubber surfaces. They contain alcohol and can cause rubber to dry or crack.