My daughter bought a used car a few months ago. The doors squeaked when she opened them so she grabbed my spray bottle of WD-40 and sprayed the bar that prevents the doors from opening too far. (WD-40 is not a lubricant. There, I said it, OK?) The squeaks went away immediately. The bars are metal, covered in plastic.
Today she told me that one door was beginning to squeak again, just a little, so I took a look in my shop to see what kind of lubricants I had lying around. I found a can of PB Blaster Silicone Spray:
The can says "This non-staining lubricant eliminates squeaking and binding and extends the life of: - Metal - Plastic - Wood - Rubber - Vinyl - Leather"
I tried the door she said was squeaking and it did indeed squeak, just a little, as it approached fully open. I sprayed the bar with the silicone spray and tried the door again. The racket was almost deafening. It was same squeak often heard from car doors, but it was the loudest squeak I had ever heard and it now squeaked the entire length of the bar, on open and on close. I sprayed the bar again and it was just as bad.
I grabbed my spray bottle of WD-40, sprayed the bar again, and the noise went away instantly. I didn't even clean off the silicon. The door is now silent.
Why would the silicon lubricant cause such a racket? Not only didn't it eliminate the minor squeak, it caused the bar to squeak along its entire length.