With so many 'BEST' threads, so much arguement that sometimes get out of hand, I decided to settle this once and for all. You never need read another 'BEST" thread. Back in July of 2008, I started a research of UOA's on BITOG. I soon expanded to searching Google and Yahoo for other UOA information. At first, I limited my research to only 30 grade synthetic oils. I also limited to Castrol Syntec, Mobil 1, Valvoline Synpower, Quaker State, and Pennzoil Platinum. I later added Amsoil because of its greater use than some of the others. Idropped Quaker State because of limited use, as least limited UOA's. I went back to the beginning of the SM certification. As the research became more intense, I started to research applications. How long was the OCI, what kind of engine was it, how was the vehicle used, what was the normal/expected RPM range of that engine in that use, what was the geography where the engine was used, what was the topography, temperature swing of the geography where the engine was used, was it a push-rod, OHC, DOHC, supercharged, turbocharged. I looked at the wear area of the engine. What was the circumference and width of the journal, bearing, cam lobes? What was the wear area in square inches of the cylinder walls? What was the piston speed in feet per minute, much more important than RPM? I got a friend, who is a chemistry professor, to help me with the results. I got some chemistry students to assist, and a couple engineering students to assist. I have well over 600 hours and my assistants have well over 900 combined hours. I was also able to have limited communication with a tribologist from one of the oil companies and more communication with a chemist at one of the blending facilities of one of the oil companies. I also know someone that has access to gas chromatography, liquid solvent chromatology, and atomic spectrograph(???). I know that there are other, very few, folk on BITOG that know to the molecular level what is in the oil that they use, but they know as I know that you can get into serious trouble, lose everything you have by giving out specifics. That is the main reason I rarely am seen on topic about what percent of what GP is in which oil, only very generally reporting what is available from PDS and MDS specks. You cannot look at a couple dozen UOA's of a given oil and learn much. There are way to many variables. One oil showing a FE level of 10 may be much worse than another showing a FE level of 15. TBN may show how much detergent/dispersant is left in the oil but it doesn't say if the anti wear is depleted, FM, and even the true condition of the base oil. Very little to be learned there. You can and should look for trends, BASED UPON EQUAL ENGINE OPERATIONAL ENVIRONMENT OF THE OIL, wear areas, piston speed in FPM, RPM, heat, geography, topography, and the many other things that have to be taken into consideration. The question, "what is the best oil," has to be qualified also. Some folk have an idea of what they want from an oil, some don't. For example, I do not want a really high detergent package for many reasons. I know an oil that meets that spec. I want an oil that stays in grade, and close to its starting 100C cSt. I know an oil that meets that speck. I want an oil with a minimum X HTHS to begin and end with. I know an oil that meets that speck. Sadly, they are not the same oil, so, I look for a compromise and I actually use a compromise because that is the oil that gives me 200,000+ and 300,000+ mile on my engines with no problems, leaks, seeps, or consumption. This oil also give us an average of 180,000+ miles before trade in. I know an oil that stays in grade better than the oil I use, but I don't use it. I know an oil that has a better detergent to anti wear ratio than the oil I use, but I don't use it. I know an oil that has a better HTHS than the oil I use but I don't use it. I use the oil that has the best combination of the three. I have not finished my study and I have not got all my ducks in a row, as of now. Hopefully I soon will or I may decide to add another variable. One of the things I am doing now is comparing GP II/+ to GP III to GP IV. If I get to release that, it is really impressive, at least to me. Advertisement and mass assertion have extremely high applications. An example, one of the most popular BITOG oils has the worse shear rate of any oil I have encountered in research. What is the best oil? That depends upon individual requirements, expectations, and standards (let me abbreviate RES). I start out looking for the best oil with the expectation that at 200,000 miles, the engine will be running within factory specks and at 300,000 miles it will be a daily use vehicle I can depend upon for whatever use. If you live in upper Michigan, or Canada, and drive 4 miles a day one way, you have different RES. If you trade at 3 years, 45,000 miles, you have different RES. If you run a turbo, Twin DOHC, V6 hard and furious, and expect to have to overhaul frequently, you have different RES. You get the idea here. I have found trends. There is one brand and grade that stays in grade better than any other. There is one brand and grade that has the best detergent/anti wear ratio (I didn't even know this existed before I started this research) than any other. There is one brand and grade that has a better 100C cSt/HTHS ratio than any other. I don't use any of these oils. FOR ME, my geography, my topography, my climate, my engines, my use, my RES, the best oil, by a good margin, is Mobil 1 15W-50. If you live in upper Michigan or Canada, drive 4 miles, one way, daily, it may be useless for you. What is the best oil? That is an easy on: it is the oil that meets your TRUE Requirements, Expectations, and Standards.