Why does the windshield feel oily and not clean when wiped?

[LylaFitz]

The windshield feels oily and not clean when wiped because exhaust fumes form an oily film on the glass, which cannot be cleaned by the wipers alone. Cleaning the glass: Wet the windshield with water, apply toothpaste to the left half, scrub the windshield with a sponge, rinse with clean water, then use dishwashing liquid to clean the right half of the windshield, scrub with a sponge, and rinse with clean water. Replacing the wipers: Generally, when the glass is not clean, the reason can be attributed to the wipers. Or the glass itself is dirty. During driving, dust in the air and exhaust fumes from the vehicle form an oily film, which cannot be cleaned by the wipers alone. At this time, it is necessary to use glass cleaner or toothpaste for cleaning, scrubbing with a sponge in a circular motion with a little force.