Personally I would not purchase newer than around 2016. Reason being that was about the last year of the M276 engine which does not have a supercharger nor turbo chargers. To me it is a lot easier to work on than the later twin turbo engines. Only thing I have with a turbo is a 1998 E300 and an 04 Ram 2500 with the Cummins.

The 2019 will be an E450 which is twin turbo, v6. If you have someone take care of it for you go for it. I have not seen anything that would lead me to believe they are not reliable if properly maintained. High mileage does not bother me as long as there are maintenance records with it.

Stay away from anything that comes out of state where they salt roads and do your research to see if they are coming out of an area that has flooded while it was in that area. Good luck finding one.

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Jim