There used to be an AWESOME diesel mechanic at Crystal Ford in Silver Spring named Mike, and the service writer was Rich. I don't know if they're still there, but it is definitely worth calling over there to see. I was wracking up MAD miles on my 7.3 and was in there 2 or 3 times a month for basic services and Mike caught a few potential issues while they were very minor before they became major fixes. I know they work on ambulances and RVs