I bought my FLD120 with a 60 series detroit engine 8 months ago.It had 1.75 million miles with no history of overhaul.The gauge now reads 1.25k. The seller always used Rotella T oil and had always done the oil analysis with nothing in the oil at speedco.Since I got the truck I have never done oil analysis but he had told me the engine would burn about 1 1/2 gallons of oil every 2000 miles and this was true.I wanted to slow down the oil burn and these guys at truck pro recommended something called "mystique" synthetic (comes in a black bottle with purple writings)oil and it comes in a 2 gallon bottle.I have been using this oil in my last interval until I went to TA for an oil change.The guy at TA showed me metal shavings and suggested an overhaul.I am not even ready for a $8000 job.I also noticed that since I went back to 100% Rotella T and Lucas my oil pressure is about 5-10psi higher than the Mystique oil mixed with the Rotella T.He also suggested I keep my eye on the oil pressure gauge and pull over when I see it dipping.Especially Bob h, do you think the Mystique was culprit or am I risking? The truck drives fine at the moment.

Switching to a Synthetic oil after it's accumulated lots of miles is never adviseable.

isnt it usual for at least a few pieces of metal shavings to be present at the tip of the drain plug? Save the shavings take them to a reputable shop and just by lookin at them they should be able to tell you what/where exactly they came from.

quite possibly normal