Tried to mail a sample at the post office today. I was all ready to deal with problems, armed with the letter from the Blackstone website. Sure enough, "what is the contents?" I told him "engine oil" "We can't ship that!" I told him that I knew there may be a problem considering that numerous people thoughout the US have had the same problems trying to ship used oil for analysis. I told him I had a letter to explain why my package was not regulated by the USPS code regarding flammible liquids. I then showed him the letter. He began to read it and immediatly blurted out - "OIL IS FLAMMIBLE!" Then I tried to explain to him (as nice as I could be) what flash point means, what a flash point has to be to be considered flammible & combustable, and how it applies to my package. I also explained that the company I work for sends an oil sample out via the corner mailbox at least once a week. I guess this was a mistake on my part - opps. He told me he turned a guy away last week who was trying to ship oil. He was getting more defensive by the minute. I finally realized I was going to get no where with this guy. I asked to speak to his supervisor. At this point he suddenly changed his attitude & said, "well, I guess we can try it - it be $1.75" I hope it makes it - maybe UPS is the way to go from now on. Blackstone obviously knows there is a problem. Why don't these labs contact the post office & straigten this out. It seems like they would have a louder voice & need the post office to work for them to stay in business.