If your engine oil is that black, I would just do an engine flush. I bought an audi one time that probably never had it's oil changed in the first 40,000 miles. It was sludged up bad, and three consecutive oil changes didn't fix it.
My ex hitting the oil pan and busting it (requiring replacement) DID fix the problem.
psted this before, but I picked up a Honda Prelude ( 88 model, with 100,000 on it ) for $2500 around 2000 or so...
had been owned by a woman and she ran Pennzoil in it...the last oil change had been at 97,000, but that had been 3 years earlier...
tuned it up and pulled the valve cover... the entire head looked like the highway dept had just paved it with fresh asphalt...
I scooped out the big globs I could get at with an old spoon... put a new gasket on it, and did an oil change of Mobil 1, 0W40 ( or 0W 30, can't remember which, but wanted to try a ZERO weight oil to see how it held up or if an engine would use it..)
Although the body was in great shape, I was concerned about the sludge in the engine, so I decided this car would be a disposable test rig... just run it until it blew up....
Never had any intention of changing the oil, just change the filter every 5K, and add as needed.... test just how good Mobil One really was in the long run...
40,000 miles later a friend was just getting divorced and wanted a car with good gas mileage and was "sporty".. so he hammered me to sell him the Honda....wouldn't let up.... was even offering me the $2500 I paid for it....
I finally let it go to him... Del is a mechanical idiot, so being a friend, I went thru the car before I turned it over to him... new tune up, radiator flush and fill, complete break job, transmission change ( manual )....
When I took the valve cover off to see what the inside of the engine looked like, after 40,000 miles of Mobil One with no changes... and only had to add oil when I changed the filter every 5K..... I was shocked at the look of the upper end of the engine...
All of that sludge was totally GONE... the inside of the engine had zero sludge on the head...had very light varnish coating, but considered what it looked like previously, I had no issue with that...
So I can verify that Mobil One really does work... that is why I pretty much run it exclusively, minus little tests I do when an engine has high miles and so does the car....
and example is on my 94 Camry.. at 310K, I filled it with Mobil 15W40 Diesel truck oil... changed the filter every 3300 miles ( 3 times in 10K) and added as needed... ran that oil 20K and then took the valve cover off to see what it looked like underneath...
that compared to what the head looked like before the change... surprisingly, 20K on 15W40 dino oil, I only saw a slight bit of varnish, but ZERO sludge build up... most of this was Highway Miles.. but I was pretty darn impressed with that...
I think frequent filter changes, on engines that are not just used for short trips, like my wife's car is...good oil can give a pretty decent life span of itself... at least the right oil will...
