Thanks guys, Larry what is CI4 oil? Also today I drove the burban, towed the boat and the noise kept coming back at idle or close to it. I also noticed the oil pressure went down to 20 on an ocassion at ilde after getting of the freeway. Most of the time the pressure was at 30 to 40 at idle and 60 on the freeway. Not sure if it makes any difference for diagnosing.
I will change the oil tomorrow but I need to understand what CI4 is.

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Thanks, Juan

It's a standard to which oils are tested. It's printed on the bottle. CI is the latest standard I've seen. Basically, good, quality oil.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

C indicates the oil spec for diesel engines. Diesel engines require lots of detergent and cleaner additives to deal with soot. These oils are also rated for gas engines and will clean them out very well.

My favorite example is Chevron Delo 400, but equally good for your purpose is Mobil Delvac which can be purchased at Wal Mart.

My guess is that you need to change oil more often.

Keep in mind that it is somewhere between very difficult and impossible, to diagnose noises over the internet, but cleaning out the engine with such oil would be a good first step in fixing the problem.

Please let us know the outcome.

Good luck,

"Gunk" makes an excellent engine flush add to oil allow engine to idle 15 minutes drain oil and remove filter. when adding fresh oil add 1 qt.Marvel Mystery oil in place of 1qt. oil + remainder of fresh oil and filter.
I have done this with 3 cars, Chevy, Volks,BMW and it has worked with each.
This problem usually happens when oil isn't changed often enough when you drain the oil after the flush you will probably see globs of sludge in the oil.
Good luck
Change it hot and change it often is a good rule.

I apologize for disagreeing. Your method will get alot of gunk out of the engine, but is quite harsh. I am inclined to go along with the flushing portion although it is not the approach I would take. What I take issue with is putting MMO in with a fresh oil change. The additive package in modern premium oil is quite good. MMO is an ancient remedy and does not work well with the modern oil additive package and will likely do more harm than good.

The safest way to get an engine flushed and keep it that way is to use one of the oils I indicate or any other CI4 rated oil. Once the engine is cleaned out use your favorite premium oil with ADEQUATE oil change interval.

Thanks for your post and have a great day,

No need to apologize I respect your input and although I am not a fan of flushing engines or of MMO these were extreem cases and the method was reccomended by an automotive engineer who was my neighbor
Flushing engines is risky and you could end up with more problems than you started with.
PS I usually only use MMO in my air tools.

Ditto. There is a can of MMO next to my tool box and my air tools get a few drops before each day of use.

There was a time when the additive package in motor oil was somewhere between very poor and non existent. In those days the situation was aggravated by colder thermostats and draft tubes allowing for more moisture buildup in engine crankcases. In those days MMO was a drastic step that had to be taken under certain conditions and was about the best we could do. There are some folks who don't realize just how drastically all of this has changed, thus they cling to the old ways.

NOW, however, engines have very good crankcase ventilation and higher temps which boil away more moisture resulting in a lot less acid buildup. Add to that the EXCELLENT motor oil additive packages in premium oils and you have a combination that will never need such drastic cleaning if the oil is kept changed.

For those drastic cases where oil has not been changed to a point of buildup, a good oil, preferably one of those I have noted, changing very often and always draining hot for an extended period of time is the best and safest step toward cleaning the engine IMHO.

The Gunk is a decent way to clean a gunked engine, but I would personally use that approach sparingly and VERY carefully as you point out.

Have a great day,