Working on a Dodge RAM. I don't know how many years since it had an oil change. Replaced front and rear axle and transfer case fluids with Amsoil. Changed oil and filter on engine, then ran it for a day and added a gallon or so of diesel to it and let it idle to further clean out the filth and goop from the engine. The original oil change oil looked like tar in color and somewhat in texture. The second oil change after only using he oil one day then idliing it with a gallon of diesel added to crankcase was pitch black, also. Added new Amsoil filter and Amsoil to engine after draining thinner black sludge garnered by cleaning the inside of the engine with the added diesel. Added new Amsoil bypass filter. Oil the next day looked kind of pale gray, not blacker than black. Turbo whistle is noticeably louder, interestingly enough. My theory was that the plain-bearing turbo was free to spin now, not slog through neck-deep tar. Pulled up to a kid with a loud gasoline Chevy pickup, put it in 4x4 (otherwiise will just spin the rear tires0 and took off from the intersection like a rocket. He pulled up to me later and asked 'WHAT DID YOU DO TO THAT TRUCK?' I told him it has a straight pipe, Predator tuner and had to use 4 wheel drive to launch it without wheelspin. The main takeaway of the oil change was the increase in turbo whistle compared to before hand with the tar-like years-old engine oil. With a plain bearing, those turbos thrive on thin, clean oil. I was surprised at how black and opaque the oil was after a day of running the engine around town, plus the idling with the gallon of diesel in it. What was telling was that with the super-fine-particulate-filter bypass filter on the truck, the oil was not the usual "pitch black the monent you put it in the motor.'
That reminds me of my first car. A 1963 Plymouth Belvedere 225 cubic inch. It had 50K miles on it when I bought it and the previous owner rarely changed the oil. After all of the oil passages were blown out, the engine ran great until I sold it four years later. That slant six was indestructible.
