A neighbor asked me this a while back. I feel compelled to repeat the story here. I worked 17 years at a large paper mill (now closed) here in West Michigan as an industrial maintenance mechanic with a heavy emphasis on hydraulics. Yes, I was the hydraulics guy. This mill had it's own coal fired power plant, 2 paper machine's, and a large sheeting facility. It used a very large amount of various lubricating fluids, hydraulic fluids, and even heat transfer oil's. Using exclusively Mobil product's from a local distributor, they were there quite often with their tanker truck. Turn over for their truck driver's seemed to be fairly high. These tanker trucks had several different compartments with different oil's in them for other customer's. As became habit with my boss, he, 99% of the time, had me adjust the in plant valve alignment to allow the tanker truck to pump our oil from the truck into our bulk tanks. They used a 2" hose about 50' long to reach our riser. After unloading our oil, the driver would shift the valve alignment on their truck to purge the hose of our paper machine lube oil with the oil for their next stop. This was supposed to happen after each delivery. One day this didn't happen. I asked the driver about this, and he said not to worry about it. Upon further questioning, he stated his next stop was the local Lincoln-Mercury dealer (this was in the late 90's) So our local Lincoln Mercury dealer that day got about 10 gallons out of their 150 or so, of paper machine lube oil in their delivery. Some customer wound up getting it in their car. I'm sure things like this happen a lot. Also after doing a particle count on the bulk oil as delivered by this distributor many times, I found it to be fairly consistently "dirty". Another incident. One day many years ago when my son was little and we were short on time, I stopped at a local oil change it quick for you place. Had my own oil because they raped a customer wanting Mobil 1 in their vehicle. I was watching this young fellow do the work, and because he was using oil/filter that I supplied, he needed a funnel. He stuck this dirty, filthy, dirt all over it funnel into my valve cover. I went ballistic! Came very close to a physical confrontation with that youngster. He didn't have a clue why I was so upset. You guy's think you're doing yourself a favor by bringing in your oil for someone else to change, look out! Watch for this! They don't care about your beloved vehicle! These reason's along with the fact that for the most part I do enjoy working on my own vehicle is why I change my own oil and will as long as I am able. Your comments and experience's are welcome!