Are you using a paste wax like Turtle wax? I use the paste once a month and Maquires spray in between. Paste wax is way better for keeping the car cleaner longer. Also, are you drying your car right away? I find that I get the spots even if I wait a few minutes. Actually, I wash the top of the car, then dry it. Then I wash the plastic cladding on the lower part of the car, then I wash the wheels.

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2009 E320 Bluetec 117,000
1995 E300D 306,000 Sold
1996 Ford Taurus LX 130,000 Sold
1985 300TD Still 225,000 Sold
2016 Ford Fusion 24,900