Rebe,

I too have a 190 with the MB Tex, mine is grey. There are 2 things I have used to clean the grime off. I have used a basic citrus based spray cleaner and a brush. I have also used Vinylex. Though it is a protectant, I have found that with the use of a soft to medium bristle brush, you get get into the texture of the MB tex. I discovered Vinylex's cleaning capability by accident. I have used it for years on my tires. When I spray it on the tires, I can see the brown dirt/dust/whatever coming off. I let it sit on the tires for about 10 minutes and come back with a rag to wipe off any excess. It leaves a very nice sheen. The same holds true for the MB Tex. I haven't tried the aforementioned 303, but I know that alot of the Porsche guys use it.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member