I was thrilled with M17, but now I am just angry - I don't know if the problem was the M18 or M17- I used it to take the oxidation off my convertible's window- It did a great job- I removed as much as I could with a soft rag- but then something weird happened- when it rained, some of the residue was washed off the window onto the fabric around it- wherever it touched I have white staining and white dots- they seem impossible to remove. I am going back to the glowing review I wrote for the M17 and change it.