Why short intervals for cleaning?

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Everybody says to run short intervals for cleaning purposes, but why? There's a set amount of additives in an oil and don't the dispersants work equally as well over the life of the oil? Isn't draining early only wasting the additives that haven't been used yet? Or does sludge presence overwhelm the add pack and deplete it that much faster?
 
If heavyly slugged, i would change filters often as they get over loaded. if only mildly varnished, leaving it in longer is better.
 
Dispersants are consumed as they work on suspending soot and other junk. They don't detach from the stuff that ends up in the filter, they're needed to keep the particulates big enough for filtering.

Hence HDEO has more of them than regular PCMO.
 
You don't lay down deposits until the oil is full of all that it can carry, then drops out what's left...aided and abetted by excessive (for the conditions) OCIs.

If you want to scavenge already laid down deposits, you need to get the new oil to pick them up, but they become "full" quickly, and will cease picking up, and start laying down their own deposits.

Need to "fill" the oil and get it out of there.

Industrially, there are technologies that trap the deposits (electrostatics, depth media, ion exchange resins) that remove the deposits from the oil continuously, allowing it to clean.
 
IMO, short OCI's for "cleaning" is a waste of good oil.

It takes time for all the additives to even activate, so let the oil do it's job.
 
Several good answers have been given. Take another angle on this. If you are in the situation necessitating engine cleaning, you already are in remedial one of a kind mode. IOW, there is nothing normal and it must be treated as an individual patient so to speak. When we say "short interval" there is a balance of course about what "short interval" means. Do we mean idle only for 15 minutes or 3000 miles?

It all depends.

Maybe make a brainstorm list of some of the variables that may effect this OCI:

1) Type sludge/varnish needing cleaning
2) Amount of sludge/varnish needing cleaning
3) age of engine
4) previous oils used
5) type of new oil going in
6) sump capacity
7) current engine tune
8) weather
9) amount and type of helper flush chemistry added
10) history of effectiveness on this engine family
11) number of flush cycles planned
 
Originally Posted By: Shannow

Industrially, there are technologies that trap the deposits (electrostatics, depth media, ion exchange resins) that remove the deposits from the oil continuously, allowing it to clean.


Maybe a automotive scrubber should be developed that cleans the oil as we drive??? Couldn't cost more than $50K-$100K, but then outside BITOG it probably wouldn't enjoy a large volume of sales...
 
Pablo brings up very good points. I could see a 3,000 mile interval, but I have seen recommendations on this forum ranging from running the engine for a few minutes to 1,000 miles. Both a waste, IMO.

Regardless of what anyone thinks of it, I believe even AutoRx recommended 3K miles for a cleaning phase, at least when I tried it (it worked for me, BTW!).
 
I dont think a motor oil cleans so well that a very short interval will do much..thus id say 3k miles would be the minimum.
 
+1
Originally Posted By: Rolla07
I dont think a motor oil cleans so well that a very short interval will do much..thus id say 3k miles would be the minimum.
 
Cleaning with oil alone is a very slow going affair in my experience. I'm at 35k now on my Jeep and the difference through the fill hole is barely noticable, and that's been with the occassional shot of MMO to boot.
 
I say the engine and oil have to be hot for a while... think a long day of driving several hundred miles (1K+ roundtrip). If you have a big road trip planned, I have no problem draining the oil before and after. Go with a decent conventional with a good add-pack (best if it is a on-sale bargain) and let it work. Getting and keeping the engine up to temp is just about as important in my (completely unfounded) book.
 
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Originally Posted By: TFB1
Maybe a automotive scrubber should be developed that cleans the oil as we drive??? Couldn't cost more than $50K-$100K, but then outside BITOG it probably wouldn't enjoy a large volume of sales...


I'll let you know if I work one out...best I can come up with at the moment is a cooling system for the filter can to keep the metal surface below the varnish solution point.

Varnish should plate out on the filter internal surface, like it does in the cold parts like valve covers etc.
 
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