Using inappropriate products to repair or clean the car.

[So]

I've been feeling poorly recently, but felt that I needed some exercise. So I decided to wash our black Range Rover myself.

It was filthy, but after an hour or so of hard work it looked quite impressive. As a final touch, I felt the icing on the cake would be a glossy sheen courtesy of some Meguiars Quick Detailer.

So I picked up the spray bottle of Autoglym Interior Shampoo instead and liberally sprayed the outside of the car with it, before smearing it about with a microfiber cloth, wondering why it wouldn't shine.

I now have a Santorini Black Range Rover that looks like someone has greased it before roasting it in the oven. It looks horrible and even re-washing it hasn't brought it up.

Has anyone else deliberately or otherwise used a completely inappropriate product to repair or clean the car with disastrous consequences?