Quote:
Originally Posted by DD931
Mac's et. al. sell it because people buy it. That's not where you should be going for advice on how to care for your engine!! I don't know why you would use non-detergent oil for break-in, either. What property does non-detergent oil have that makes it desirable for break-in use? Wouldn't the detergent action of the detergent oil keep fine wear particles in suspension better?
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Non-detergent oil allows the rings to seat with the aid of the generated particulate where the high spots in the cross hatch are getting sheared off. Detergent oil actually carries away particulate that can be useful during the bedding in process and holds it in suspension. That isn't always a good thing while bedding in an engine. Particulate in suspension is what may damage your bearings to some degree. I'd rather have it in the bottom of the oil sump than flowing along with the oil. Once the engine is bedded in there is no further use for a non-detergent oil.
In aircraft engines, it is used just for that purpose and is recommended by the manufacturer unless it will be harmful to some other component like a turbo charger. The first oil change is performed after 10-hours then at each 20 to 25-hours after until the engine has reached 100-hours since overhaul. Back when channel chrome plated cylinders were in use, the piston rings would never break in if detergent oil was utilized.
There is a reason that the crankshaft has those sludge chambers inside the crank pins. The heavier particulate in the oil is thrown outward by centrifugal force so it won't venture into the bearing areas. This is a good reason to make certain that these chambers are thoroughly cleaned out during the overhaul process.
These old engines were intended to be maintained by regular oil changes at much lower scheduled mileage intervals than we use on modern vehicles due to the bypass filtration system. The oil being changed while still hot after a good run is what gets most of the particulate out. The sump screen and the filter just get the big chunks. The rest of it stays in suspension until you dump it out of there. As was mentioned previously, the suspended particulate is so microscopic that it generally won't even affect the oil film build that is being forced through & between the bearing surfaces. If the particles get large enough to scuff or scratch the bearings then something is already wrong.