I bought this along with their M40 (regular strength) in case it was needed. I used it on another older car and it was great and took less time than using M40. I prefer to to have both. If M40 is not strong enough, out comes this M39.  So you should own both. It is best to use, in my opinion the weakest strength product if you can. Many people said this M39 is great for removing wax that got on the black vinyl, and it is, but in my case the M40 was fine for our new SUV.