Originally Posted by Elk
Plus, checking a dipstick is much quicker than running the "oil check" on the car, and I get to see the oil.
Your visual inspection will mean nothing, unless you have special eyes that can see different spectrums by which to judge an oil condition.
If you believe that one should change oil when they simply "feel like it", then that as unsubstantiated as you believe BMW's recommendation is, even more so.
I'll go with the sensors and BMW's testing over someone's "feelings" any day.
Also, the system doesn't wait until 15K or 10K or 20K. It uses many parameters along with the sensor by which to make a determination as to when the oil needs changing. If the driver does daily 5 miles commutes and doesn't get the engine and oil hot enough, the system will trigger for an oil change much sooner than 15K.
When to change the oil is variable from car to car based on how it's driven. Going by "feeling" is pointless as it uses no reference points at all, other than the marketing of the quick oil change industry that convinced the majority of needing a "3000 mile" oil change.
That industry needed people to believe their marketing as it directly affected their bottom line.
BMW has a vested interest in their cars running longer the 100K miles.
Perception of quality is important to sales. BMW certifies certain cars and warranties them for 100K miles. Does one really believe that BMW doesn't care if that car can go beyond that mileage marker?
If you believe it you're kidding yourself. If BMW engines started dying soon after 100K miles it would quickly become public knowledge and that would affect BMW's new car sales. Yes, they are a company out to make money, and to make money they have to continue to sell NEW cars, and to sell new cars their brand has to be viewed as capable.
Synthetics easily out do non synthetic oils, not be a little but by multiples. It's proven. Does that mean every car that uses synth can go 15K or 20K between changes? Of course not, because oil change interval is conditional based on how the car is driven. Thus, the sensors and CPU algorithms use driving data by which to give an oil change time.
It's not a "feeling" or a "guess". It's based on researched science and data.
Does BMW have proof for their method?
You bet they do. It started at least by 1999 when all their cars switched to full synthetic and oil condition sensors and algorithms. Thus, it's been tested for well over a decade and evidenced by the fact that BMW engines do NOT stop working after 100K miles. There are plenty of 1999 and up older BMW will well over 100K still running strong even though their oil was changed when the car computer said to do it.
Again, its' not based on speculation, but on science, testing, and evaluation.
On other important factor is that BMW engines tend to have a much larger oil capacity than other engines.
The NA 3.0 uses 7 quarts of oil. My N54 twin turbo and the N55 twin scroll use 7 quarts of oil compared to Audi's 2.0T that has a 5 quart capacity. Thus, the typical BMW 6 cylinder uses 50% MORE oil in it's engine than Audi's. Just by virtue of capacity, a BMW engine's oil change interval can be 50% longer. If Audi has 10K for it's 2.0T, then 15K for BMW's 3.0 sounds about right.
But, all is not equal, and we can't only use oil capacity as a comparison data point. The engine build and it's cooling system will also have a great impact on the oil quality. There are many factors and all must be considered. Looking at your oil, smelling your oil, tasting your oil, will tell you very little in terms of how well that oil is working and how much longer it can still go. Many people think that dark oil means it's going bad. The truth can be far from that. Dark oil also indicates the the oil is doing it's job in keeping small particles in suspension, thus it looks dark.
Have you ever changed your oil and then after only 1000 miles looked at the color of it on a dipstick only to find how darn dark it is?
Does that mean you should throw that 1000 mile old oil out?
Also consider the environmental aspects of changing oil too soon.
Sure, it may give one a "sense" of security and insurance to change sooner rather than later, but then you may be throwing away perfectly good oil just for a fuzzy feeling. That fuzziness costs in oil, time, disposal, and effort, when it may not be necessary. Thus, it's wasteful, and that's not a good thing. No warm fuzzies there.
I understand that many new to BMW may question this extended oil change interval. But it isn't being used on a whim. There are reasons for why it's a viable decision, and one should take the time to educate themselves on why, rather than be negative on it right off hand, and then speculate and diatribe as to why their position is correct.
There is a good way to find out if you should change sooner rather than later, and that's by doing an oil analysis from time to time.
Be careful though as I've seen people send it oil after their engines are only 5-7K miles old and the report shows an increase over normal of certain materials and chemicals. However, that's to be expected as a new engine will have different characteristics than an older engine, and the oil chemistry will change over time. BMW and other auto makers know this and they account for those conditions in their oil change interval estimations and recommendations.
Feelings are great in regards to puppies, girlfriends, movies, etc...
But when it comes to things automotive and mechanical, I'd much rather go with science and data. YMMV.