So, mine was purchased new, and has almost 90,000 miles on it. Do it or not??

Y'all are confusing me...

LOL
It all depends on how you drive it! If you have a habit of "stop-n-go" traffic driving & never letting the engine warm up before putting it in gear since you bought....well then you've got a sludge build up in there already! Now if you allow it to warm up & then drive long distances with it....well then you've got virtually no sludge build up at all. Sludge is caused by condensation in your oil. The condensation comes from your engine'* temperature when it'* shut off. Short driving trips never allow the engine to properly warm up, thus it causes condensation (sweat) to form in the oil when the engine is turned off. Remember the engine'* oil actually "Cools" the engine too! The first quart or Liter is for lubrication, the rest of the oil in the system is for cooling.

I do rush hour getting home every morning, but I also have remote start, so it always gets to warm up. I may give it the "double oil change" suggestion from earlier. My oil always stays fairly clean looking, so I doubt it'll hurt much.

Oil boy~~I have less then 300kms on my rebuilt engine. I should change it at 500kms right? with a full synthetic? or what?

How about letting the engine sit for a few days, and draining it, and then removing the oil pan, and scraping the sludge, and metal out of the bottom. I did that twice to a dually I had a long time ago...

well i think im just gunna stick with regular oil changes!
I bought 4 liters of Quaker State Higher Milage tonight for next week when i go to do an oil change, and as usual im gunna buy an AC Declo filter!

lol... quaker is good at that sort of thing... like there 4x4 oil ...

Don't worry about the black color of your oil. After a few hundred miles it will always look like that.

If you are really concerned, why not get a oil analysis done? Blackstone Labs (www.blackstone-labs.com) will give you a good analysis of whats going on. Send them a little sample after you change the oil (or give the little bottle to your mechanic to fill up) and see what they say.

The oil turns "black" not from mileage, but from HEAT! Your engine temperature can change the colour of the oil. Nothing is damaged, it'* just a reaction to the temperature.

Also on a rebuilt engine its not getting up to operating temp. My oil is still clear almost.

didnt someone suggest a better way to clean a sludged engine by simply changing the oil like every 1000 miles for a few times, make sure to use a high quality detergetn oil and good filter, always changing it when hot? I coulda swore I read that here