Q: How problem free is the Ford 3.2L Turbo Diesel compared to the Mercedes 3.0L Diesel used in small RV's?

Personally I would take the Mercedes over the Ford, but the truth is, diesels are undergoing a massive engineering revamping of their emissions systems. Emissions on diesels is new to the automotive market making these systems problematic until the manufacturers figure out what will work best out on the roads. All the manufacturers are trying different systems. Mostly they are the same, but they are accomplishing the Federal requirements in different ways. Of course I am assuming your are asking about diesels that are newer than 2007 to 2010, which is when the emissions systems on the diesel were rolled out.

If your looking into anything older than 2007, my answer will change based on the decade. I would choose the Mercedes unless were talking about mid nineties and earlier. In which case, finding parts and maintaining older Mercedes motors is more difficult than an older Ford diesel.

The short answer is yes, Ford will likely have issues as well. If your looking at new off the lot, that might be your best bet because all the manufacturers are digging deep to improve the reliability of these systems. They have been forced by the EPA to begin rolling out these systems in 2007.

Good luck!