Good Morning All; The recent thread about what mechanics know about oil made me think - what do the vehicle manufacturers (or even the oil manufacturers) know about oil? The vehicle manufacturers all set oil change intervals (or let the dashboard computer do it) based on the use of the specified oil viscosity and API grade, and dino except for high end cars. Even for severe service these intervals are working out to more than 3K miles / 3 months on new cars. From the posts I've read here, UOA has been showing thinning, wear, TBN loss as early as (or earlier than) 3k. For that reason many posters here still strongly support the 3/3 plan for dino oil, or use of synthetics. So my question is, the manufacturers HAVE to know that the oil is being affected, and that wear is occurring...but what level of thinning, TBN loss and wear is acceptable to them and why? The first instinct is to say "they only care about getting you through the warrantee", but I think that might be unrealistic, there has to be more to it. Companies have to be looking longer term than that, especially the ones whose success has come from a reputation for quality and longevity (Honda, Toyota). On a related note, what do the oil makers know? The dinos mostly still push 3k/3 months. Is that because they are being realistic about the quality of their products or to get more sales? I was running M1 and called about the nebulous info on their web site, which says to change at "maximum mileage or time" in your manual. Their techrep said I could run M1 for a year regardless of how much short-trip driving I did, but some UOA posted here says otherwise. To make matters even more confusing the M1 web says it's ideal for cars with oil change monitors - so does that mean go by the oil change monitor, which could go off at 4K or by the "max mileage or time" (7500 or 1 year)? Likewise, Amsoil puts out the blanket statement about the 1 year/25K, but posters here have cited UOA that suggests otherwise in certain situations. Again, the question - how much wear/TBN loss/thinning is acceptable to the oil makers and why? How high are the "minimum" standards for vehicle and oil performance in the eyes of the carmakers and automakers? Are they high enough? Sorry for the long post. I'd appreciate your thoughts on any or all parts of it. It seems like this board is out on the leading edge when it comes to oil.... Maybe we shouldn't even go into filters Matt (sitting on the mountain looking for the meaning of life, I mean oil).