I used a clay bar on my 3 last Fall, right after I bought it, and you'd be amazed at how much crap came off the brand new surface. I also used the clay on my wife's 2004 Honda Pilot and after claying the whole vehicle and then throwing on a couple of coats of Zaino our vehicles they were so smooth that the neighbor guys were all coming over to check 'em out and were tracking down clay bars for their vehicles too! I HIGHLY recommend it be used at least once, if not twice or more, a year.