Brand new air compressor trips onboard breaker on start
I would return it.  It doesn't sound like a lubrication issue - it sounds like either the motor soft starter is bad, is not well paired with the breaker, or is simply not present on that model.  AC motors can pull substantially more current on initial start, and I'm guessing that is causing the breaker trips. I don't mean to knock Harbor Freight (much), but higher quality compressors of that size and capacity aren't usually that much more expensive.  You can obviously do an exchange and hope for better luck with a replacement unit, but if you are planning on any serious use of it, reliability is a huge plus.  Nothing destroys a work plan for the day like having a bunch of air tools that you can't use because the compressor won't start.