Break In Oil Sequence Idea

[OK-944]

(as posted in 911 engine rebuild section):

Not for a 911…but for my 87NA 944, the engine from which I’ve just finished rebuilding - top to bottom, all seals, bearing shells, rings, etc.

I also did a DIY (alusil) cylinder reconditioning process with Sunnen AN-30 paste…and while I won’t go into detail about this here, I will say that getting rid of the AN-30 residue was a total b*tch - and I’m actually a little paranoid that I may have left some behind.

So here’s my idea…that I begin the engine break in process with a DETERGENT oil - and do the first, 20 minute high idle with this, then dump this out and go to a NON-DETERGENT oil to take on the road to set the rings…followed by the usual 500 miles, another oil dump/fill, etc.

While I know that detergent grade oil is not recommended for the ring setting process, my fear about going right to a non-detergent oil for the first idling run is that this might facilitate some unwanted abrasive action of any leftover Sunnen paste residue.

My question then…assuming that detergent oil would indeed help get rid of unwanted residues more effectively than non-detergent, is would this procedure in any way compromise the next, non-detergent oil process of breaking in the rings?

[9FF]

The detergents in oil don’t remove or wash away any particles that your filter doesn’t catch, quite the opposite actually, they hold the particles in suspension in your oil to prevent sludge. So those particles are constantly circulating throughout your engine.

[OK-944]

...but if the detergent oil is then drained after the initial 20 minutes of idling - wouldn't the suspended particles be likewise drained away? Or are you saying that the non-detergent oil would more specifically leave those particles trapped in the filter...whereas detergent oil would keep these particles circulating? I cannot quite wrap my head around this.

[9FF]

Originally Posted by OK-944

...but if the detergent oil is then drained after the initial 20 minutes of idling - wouldn't the suspended particles be likewise drained away? Or are you saying that the non-detergent oil would more specifically leave those particles trapped in the filter...whereas detergent oil would keep these particles circulating? I cannot quite wrap my head around this.

Yes if you drain the oil the particles will go with the oil. All I’m saying is the detergent only captures particles too small for the filter to capture, it’s only just us to stop those smaller particles sitting on engine surfaces and building up to cause sludge in the long-term.

Btw I think your process sounds fine.

[walfreyydo]

My break in (new filters with all):

1st change: First startup, idle for 20 minutes (cheap, generic brand Oreily's oil)
2nd change: after 50 miles (rpm under 3k, cheap oil)
3rd change: after 250 miles (rpm under 4500, cheap oil)
4th change: after 500 miles (cheap oil)
5th change: after 2500 miles (good oil)

normal intervals after.

Its, of course, normal to have metal particles on a rebuilt engine, which is why you want to flush them out via oil change. I dont think it matters much if you use a detergent vs non-detergent oil, what Ive read says using non-detergent oil is an antiquated practice. I honestly dont think it matters much. Ive never used the paste you are referring to so I cannot comment on that.