RE: Too much oil.
Yes, I actually break my engines in using 18% oil and switch to 12% after a few tanks full.
The extra oil *is* helpful during the break-in process as it ensures that there''s a huge margin of additional protection available to allow for the tight-spots that will inevitably exist when an engine is brand-new.
I''ve noticed no loss of compression after changing to 12% from 18%.