I did a "Break-in" oil change at 2000mi, estimating that I would change it about every 7000mi thereafter. At just over 9000mi, the vehicle indicated it was several hundred mi away from needing an oil change. I had it changed (as part of maintenance program). My SA said he was seeing diesels every 8500-10,000 mi due to the onboard computer requesting it. I was planning on a 7000 mi interval anyway (which is about what I do on my 5er, and the diesel operates at higher temperatures and pressures), but it is good to see the computer agree.
I'm not sure exactly how the computer recognizes that it needs an oil change. I would think that in addition to oil level sensor there is an oil quality sensor which at least checks conductivity (as the oil degrades I understand it gets more acidic and thus conductivity rises). It is not a simple mileage count like on other makes (e.g., toyota).
As an aside, has anyone seen the new ford super duty trucks? I saw a review on autoblog and noticed that they put the DEF input right next to the fuel input.
http://www.autoblog.com/photos/2011-ford-f-series-super-duty-first-drive/#2778910
Kestrel,
Did you reset your service interval when you did the oil change? If not the computer has no idea you did change the oil so is still running from zero miles.
We need to get some input on what drives the service interval, but I doubt it will be the oil level or some other more sophisticated oil sensor or oil analysis. I beleive it will just be how hard you drive the "D" in regards to engine rpm, miles, acceleration, and perhaps temperatures (of what I don't know). Acidity should not actually increase since the additive is in there to neutralize it. What you look for is how much excess additive (TBN) is still in there to react with the acid forming products of combustion. That is why typically you don't want the TBN to drop lower than 50% of new oil. Once you deplete the TBN then the acids will be able to attack engine parts.
Oil level most likely will only active your SES or Check Engine light, i.e. an idiot light.:slap:
As for the DEF, I think BMW did this as an after thought since they weren't originally making these cars for the US Market, no DEF in the rest of the world.
The Ford was made for the US Market from the get go.