Originally Posted By: Pop_Rivit
How much machining junk gets left in GM engines? And do GM engines have an extreme amount of wear in the first few miles? And is the oil filtration system so poor that it can't catch all of this excess machining junk and metals that are being shed?
I've always followed the manual, which hasn't called for an early oil change on any new car I've purchased in the last 20 or 30 years. But I haven't owned a GM, so perhaps they're still like the engines of the 60's and 70's that had early oil change requirements.
I'd be more concerned about a manufacturing process that is so bad that it leaves machining junk in a new engine, and quality that is so poor that excessive wear happens on a new engine.
Do you suspect the same machining/quality issues with the transmission and other systems that use fluids, or is this limited to just GM engines?
Modern engine are built to fairly fine telerances and don't require that same type of restricted use break in period as older engines did. All the components are cleaned before and after final assembly, so there is not much debris in the sump of a modern engine during break in. About the only debris I can think of might be excess sealant around some gaskets, but that is of no significance apart from showing up as Silicon in a UOA for some time.
Transmission fluid is very different to engine oil, as one of the main concerns is just dirt rather than wear metals and it's not subject to much high temp shearing.
UOA for new engines can still show extra break in wear for quite some time, so it is the trend in wear metals that is important.
