You can use regular glass cleaner on the inside of your car windows, but it’s a bad idea for the exterior and can cause long-term damage to other interior surfaces. The primary risk comes from ammonia, a common ingredient in many household glass cleaners like Windex. Ammonia can chemically degrade the polyvinyl chloride (PVC) and plasticizers used in car dashboards and trim, causing them to become brittle and crack over time. For exterior windows, the issue is the hydrophobic coating; many modern cars have a factory-applied water-repellent layer on the outside glass that ammonia-based cleaners can strip away, reducing visibility in rain.
The safest approach is to use automotive-specific glass cleaners. These are formulated to be ammonia-free and safe for all interior surfaces while effectively removing the unique grime found in cars, like off-gassing film from the dashboard.
| Factor | Household Glass Cleaner (e.g., with Ammonia) | Automotive Glass Cleaner (Ammonia-Free) |
|---|
| Interior Plastic/Trim Safety | Can cause drying, fading, and cracking | Formulated to be safe for all surfaces |
| Exterior Glass Coatings | May degrade water-beading hydrophobic layers | Designed to preserve these coatings |
| Effectiveness on Greasy Film | Less effective on dashboard off-gassing residue | Specifically designed to cut through this film |
| Streaking | Can streak more easily on large, vertical auto glass | Often includes anti-streak agents for better clarity |
| Cost & Convenience | Cheap and readily available at home | Requires a separate purchase (approx. $5-$10 per bottle) |
For a professional result, use a two-towel method: spray the cleaner onto a clean, soft microfiber towel first, then wipe the glass. Use a second dry microfiber to buff away any residue. This prevents overspray onto your dashboard and ensures a streak-free finish.
