I just bought a used E (45,000 miles) on Saturday and love it. After I got it home, I noticed all the door hinge rubber was brown. It's like talcum powder from road dust. I've gone on camping trips before so no big deal. I can clean it up. Then I was looking underneath and noticed caked mud everywhere. I grabbed a bit and it crumbled into that fine powdery dust. Why I didn't see it when I bought it is beyond me. I took it to a car wash and got the big stuff off and there are no scratches where it had settled and the parts cleaned up nicely. It looks like dust had accumulated there over time, got wet and caked up. I hate to let it sit in there and trap moisture. The dealer asked me to bring it in and they'll clean the undercarriage for me. The E had lots of new parts like tires, rear brake pads etc. They also changed all the filters, fluids etc. They also replaced the a/c condensor so I'm wondering if dust was the culprit? maybe the original owner lived on a dirt road? But the windshield and paint etc. have absolutely no dings so who knows. I've never heard of dust shortening the life of a vehicle but should I check on anything else while I'm "de-dusting" it? Don't get me wrong, I've got plans to drive it and get it dirty myself but I paid a few bucks for this vehicle so I'm going to take them up on their offer to clean up the undercarriage.