One thing to remember is that for most operations, even at sea level, full
rich is too rich. Consider this: The full rich mixture setting must not be
too lean for any condition likely to be encountered, as the pilot obviously
has no way to further enrich the mixture. But at -30 C at sea level (a temp
sometimes seen in winter in many parts of the country) and barometric
pressure of 29.92", density altitude is MINUS 5900 feet! If full rich
mixture is not too lean for those conditions it sure as heck will be too
rich at sea level in standard conditions. I'm not advocating leaning for
takeoff at or close to sea level, as a rich mixture may be required for
adequate cooling, but I always start to lean fairly early in the climb.

-Elliott Drucker