I love this topic.. Always a lot of different opinions, methods, and conception on why or when one's oil should be changed. There is only 1 wrong way, and that is when you never change your oil for the life of your machine, which is probably going to be short.
There is a lot of misconception on what is really happening to your oil as it lubricates, protects and cools your engine, or why does it get black, and what exactly is the oil filter doing to help my oil??????? I will try and explain to the best that I have understood and learned from my favorite Uncle, Uncle Jett, which is a Petroleum Engineer, Graduating from The University of Texas, and employed by Exxon for 29yrs in there research and development department(not really a department but something similar) there almost like a sister company to Exxon, carrying the Exxon logo, but showing on letter head "Advanced Research and technology of deep well petroleum(deep well is where all engine oil comes from)- A Exxon Company"
Sounds important to me. LOL. what they are trying to do rite now is to develop a oil that will shed 90% of it's contaminants, meaning the stuff that breaks down your oil, and the few things that make it black will no longer be able to mix with the oil, therefor letting the oil filter finally do what we all think it has been doing since oil has been used for lubricating a combustion engine. lol. The reason for the quote I posted is that the Camaro man got it the closet to the correct answer from the original question. "How often should I change my oil". And here is the break down: #1 factor in oil contamination is the carbon in the fuel we burn, and #2 is the temperatures at which the oil is subject to, very little is to blame on engine debris(the ultra fine metal dust that exists from metal to metal wear) Oil kind of acts like a mop, as long as the mop is not full of dirt it will keep picking up dirt, but as it gets closer to being full of dirt it will not pick up the dirt as efficiently. The black that we see in our oil is mostly, liquified carbon it is so fine, and the other portion of the black we see is caused by the heat the engine produces. Combustion chamber temps are actually slowly scorching the oil. Kind of like when you accidentally leave the stove on after making bacon, and you come back to a blackened mess in your wife's pan. So, Like the mop, when the oil turns black it is full of carbon and like the pan, scorched oil is not going to lubricate anything(try making some fried potatoes in that scorched pan)LOL. There is going to be a fire. LOL.
So if your changing your oil before it gets dark then it's like ringing out the mop just after a few strokes. If your using synthetic oil and you are still using it long after it has turned dark, (because it's SYNTHETIC) You are adding unnecessary wear to your engine with the carbon content of the oil being well over the limits of the oil. Synthetic oil was developed to reduce the amount of time it takes for the oil to scorch, thus giving it a higher temperature classification, and increasing the overall life of the oil based on scorch reduction only. So Synthetic is better, but for only 1 of the 2 major factors discussed.
The carbon issue is what there working on and have been working on for some time now. Uncle jett doesn't think it will be to much longer that we will see engine oil lasting 30,000 miles before it is full of carbon(dark) (and like the mob). Carbon shedding or shearing is what there calling it(TOP SECRET stuff). Like I said before, the oil will not have the ability to attach itself to the carbon, and therefor the oil filter can pick up the unattached carbon, therefore increasing the overall life of the oil based on carbon reduction only. Now combine this new technology with the technology already being used in synthetic oil, and engine oil will be revolutionized. Carbon free! and Heat resistant!
So here it is in a nut shell for all you "over excessive oil changers", all you "under excessive oil changers", and all you "BIG BEN/ Ramon calender oil changers". If you think you must because you will not sleep well if you don't by all means change your oil, and if you think because you paid $8.00 a quart for synthetic and you feel you need to get your moneys worth out of it by all means wait until it is black as black can be to change it. or if you are convinced that the manufacture's time or mile intervals have to be the best way because that's what Honda say's then by all means go by there guide lines. But if you want to get the Maximum life out of your oil because 29yr oil veteran/ Exxon petroleum engineer say's it's all about the COLOR then by all means follow Uncle Jetts advise. "As soon as it turns light black to med light black, it's done(full)."
Filters:
The oil filters we use on todays engines are 100% better than they were 30years ago, but they are still mainly only catching metal debris, and very little carbon. The carbon is being caught by the oil instead, because the filter cannot catch something that is permanently attached to the oil. This is why even after the oil has sat in a drum for a 100 years it is still black, so how can a filter get something out that wont even break down or separate after a 100 years. LOL
A high amount of carbon in your oil is like taking 2000 grit sand paper to every metal to metal connection in your engine, thus slowly sanding your tolerances out of there service limits.
Hope this clears up some of the misconceptions about engine oil. and hope I didn't confuse anyone? questions and comments are appreciated.