Synthetic oil ?

Is the question geared towards a washing of crud issue?
Like in changing from a non-detergent to a a modern high detergent?
As far as lubricity goes goes, I see no reason to fear switching from a Convential Oil to a Synthetic Oil.
Even more so on a rebuilt engine.

Is the question geared towards a washing of crud issue?
Like in changing from a non-detergent to a a modern high detergent?
As far as lubricity goes goes, I see no reason to fear switching from a Convential Oil to a Synthetic Oil.
Even more so on a rebuilt engine.

Jinin, isn't detergent oil is good in our old cat engines?

Larry, I just rebuilt a KTM 4 stroke motorcycle engine. It has about 30 minutes on it since being rebuilt. Would you recommend I drain the synthetic oil and fill it with regular oil until it's broke in?

Michael,
Drain it, and refill with some 20w non-detergent oil. The high detergent oil, will glaze the cylinder wall, and not allow the rings to seat.
My friend the dirt farmer, used to run roundy cars, using the 2.3 ohc Ford engines. He always used hi detergent oil, and you could always tell which car was his, from the blue plume from the pipe. He rebuilt the last one, and made a paste of Bon Ami, and 30w, smeared it on the pistons, assembled the engine, end of problem. When he was setting it into the chassis, he hooked up the battery, and hit the starter switch, and after about three revolutions, it had so much compression, it worked the starter hard to make it turn over.

All I'm saying is you take a 70 year old engine which had non-detergent oil ran in it which will have years of crud in it. High Detergent Oil will wash this crud out of everywhere, hence loosening the tolerances built up by the crud. You may have increased oil consumption, didn't say "will have".
There have been numerous discussions about Oil to run in the old tractors and this is always part of the discussion. Most tractor engines have standard Cast Iron rings which require way less break-in running to seat.

As far as a FORD racing engine, it probably ran Chrome Rings for reduced friction and heat which are very hard to break-in especially in a Race Car application.

Then as far as using a "Non-Detergent" oil to break in an engine, do you guys honestly believe that every MAJOR engine manufacturer follows a regimen such as that?
NO, THEY DO NOT!
The oil that is put in the factory for "run-in" is the same oil that the engine will be shipped with.
If it calls for an extended life multi-weight detergent oil that is what they put in.
If you drive a automobile and it comes from the Dealer stating it has Synthetic in it that is what was put in at the Factory.

Even CAT puts in standard lubricants at the factory, only difference is they put a Dye in to use with a black light to find leaks.

As far as dirt bikes,I have been racing a rebuilding for them 30 years with both kinds oils with the same results! I've done top ends dry and wet with spec compression readings after one running cycle cool down re-tourqe.
But I'am new to diving deep into dozers and there is all new set of rules to follow for diesle engines! I'am trying to figure out what info I can transfer from gas engines to diesle.

All I'm saying is you take a 70 year old engine which had non-detergent oil ran in it which will have years of crud in it. High Detergent Oil will wash this crud out of everywhere, hence loosening the tolerances built up by the crud. You may have increased oil consumption, didn't say "will have".
There have been numerous discussions about Oil to run in the old tractors and this is always part of the discussion. Most tractor engines have standard Cast Iron rings which require way less break-in running to seat.

As far as a FORD racing engine, it probably ran Chrome Rings for reduced friction and heat which are very hard to break-in especially in a Race Car application.

Then as far as using a "Non-Detergent" oil to break in an engine, do you guys honestly believe that every MAJOR engine manufacturer follows a regimen such as that?
NO, THEY DO NOT!
The oil that is put in the factory for "run-in" is the same oil that the engine will be shipped with.
If it calls for an extended life multi-weight detergent oil that is what they put in.
If you drive a automobile and it comes from the Dealer stating it has Synthetic in it that is what was put in at the Factory.

Even CAT puts in standard lubricants at the factory, only difference is they put a Dye in to use with a black light to find leaks.