I have read in the past year some debates about how clean new oil actually is and where to buy it. I recently had some work done at Chevrolet dealership in the midwest. They have quite a few dealerships in three states, and sell/service Honda, Kia, GMC, Buick, and GMC. They offered a complementary oil change so I took them up on it. I asked and they freely provided a sample of the oil they use. I was told it was AC Delco Full Synthetic Dexos 1 Gen 2 oil, API SN. They even took a picture of the 500g storage tank for me. They said it was the same oil and nothing to worry about. I went into the parts department and bought a quart of the same AC Delco oil (p/n 88865926) 10-9253. I sent a sample of each to Polaris Labs and paid for the ISO Code particle count, in addition to the normal tests.. Attached are both new lube references reports. There is difference in additives, especially Boron and minor difference calcium, phos, and zinc. The shocker was the particle count. The oil they have in bulk storage and which they use for their express lube service was 32x more contaminated with hard particulates than what you would see in a quart bottle that was produced by ExxonMobil in their blending facilities. I went back a few weeks later and saw, a third party distributor delivering new oil. When one considers the the distribution channels, storage facilities, vehicles needed to transport the oil to it's final destination, the chance of contamination is quite high and probably normal for the industry. I doubt they clean any of these tanks, rather just drain and refill, especially for delivery vehicles. I thought maybe there was some error in one particulate size or the test in general, but each micron rating showed the same percentage of contamination per ISO Code when compared with the oil in the quart container. When you consider that anywhere from 10-20% of oil may remain in the engine, and how fast or how little they allow the oil to drain, along with the high contamination of oil going through the distribuition chain, gives me a different sense of "trusting the experts, and doing my part maintaining the car the best I can." Makes me wonder if the quick drop in TBN after an oil change oil is really normal or due to conditions described herein. . The old adage applies, if you want it done right, do it yourself, and "buy it yourself." Yes, I have had bad experiences at dealerships and some indepedents with oil filter and drain plug installs, but none when I do it myself. I always watch to make sure they actually change the oil and filter. If you use an independent, ask them if they buy their drums of oil direct from a reputable blending facility, distribuition facility, or have them refilled on-site. The other choice is to buy it yourself by the quart or gallon and have them change it.