If you call a few auto parts stores around you and ask for a WIX 24077 oil test kit and buy it,
it'll have address labels inside one, US and the other in Burlington Ontario, Canada.
Shop around a few store for different prices, you could get it for less. I've been using
it for 4 yrs.
I take the oil sample, fill out the form, put in the outer container then pack in a
padded mailer and send it, results in a about a week. Costs about $25 for the kit and $10 to mail.
I don't use the outer container bottle as a mailer, might get buggered up by the mails.