http://pe.usps.gov/text/dmm300/601.htm#wp1065036
See section 10 for some light reading.
...
Maybe 10.13.3.b specifically.
I think this says its ok, ha.
The local post office here does not have a problem with full metal qt. oil cans, I have asked.

[This message has been edited by tokheim (edited 02-15-2007).]