I am in the frozen north of Canada (91 deg F today in American English!) so I sent my oil to a lab here in Acton, Ontario. Cost me the grand sum of 25 bucks and they completed the test and faxed me back the report within 5 days of mailing in the sample.

My brother - who maintains marine diesels and generators - recommended the lab. He uses oil tests as part of regular maintenance programs.

Amsoil do this in the US but their service is quite pricey, IMHO. I suggest you do a Google search or check out your yellow pages under lubricants or fleet services.....