SiK182

Doubt it can harm the plastic, but I just wanted to make sure..

Pinky

Safe hell no!!!!!!!!

Pick up some Plexus.

pellisS2k

plastic does not like ammonia.

eyedrj

Try using Eimann Fabrik Clear Vision OR Stoner's Invisible Glass .. they work great.

Argetni

Just use Plexus

William

Windex is formulated to clean glass (ammonia and other agents). The rear window is made of vinyl. Glass has a hard nonporous surface, vinyl is soft and porous. Never use any glass cleaners on your rear window.

Lovetodrive2000

Plexus for weekly cleaning, and 3M plastic cleaner and polish for if it gets cloudy,

Never, never use Windex!!!

Penforhire

Put down the Windex and nobody gets hurt, grrr. Seriously though ammonia is rough on all sorts of materials, most definitely including your back window! Go for the Plexus or Novus plastic cleaners. They are "da bomb."