Today rain caught me and while the wipers swept I noticed the windshield is blurry, so the visibility was reduced. It is perhaps because of oily spots. What solution should I try to remove this problem?
Thoroughly clean the glass, both inside and out. There are many different glass-cleaning products out there - have a look in the cleaning aisle of your local store. Try and find something that doesn't leave a residue.
Once you have cleaned it, immediately replace your wiper blades. These should be replaced every 6 months or so as a matter of course.
If you're in a colder climate, try to avoid wiping the inside of the screen when it has steamed up, as this can lead to a build-up of grease on the glass. If you have to wipe it, use a clean cloth and keep it clean, but it is better to use the demister.