Unless I missed it somewhere....I did not read where you used an engine flush before switching over to synthetic....?? When I switched my diesel engines over from conventional to Amsoil, I was told to use the engine flush that Amsoil sells to help clean up the cylinder walls and all from the contaminants.

They said to pour the flush in with the conventional oil and run the engine for either 20 or 30 minutes (cannot remember) and (do not drive with the flush in the engine) but after the run time, drain the engine and then put the new synthetic oil in and my engines always looked clean when checking the oil.

One main thing I remember when I switched was that the engine temp. always seemed to run about 5° cooler with the synthetic over the conventional oil......