'98 Mercedes M-Class. It actually checks conductivity of the oil. I argued with my mechanic that no one does that, it just ranges from a mileage meter, to a computer system that monitors engine hours, warm ups, and idle time, things like that.
He was a factory trained mech. He used to run the shop at the local dealer, but the dealership screwed around and Mercedes took his franchise away.
So, my guy opened his own shop specializing on Mercedes and other foreign models.
I was bothered by the fact that the oil change default setting was 10,000 miles. In other words, when the mileage was reset, it came up as 10,000 before the next change.
He pointed out that the 6 cylinder in that car used 8 quarts. In other words, it had a built in oil change.
That makes sense I suppose. Modern oil does not "wear out" as much any more, although there is some loss of additives. The biggest reason for an oil change is due to contaminant.
And 8 quarts is going to take longer to build up bad stuff than 4 quarts would.
I guess if you built an engine that had a 100 quart oil pan, you would only need to change the oil every 100K or so......
But, then I noticed that the service mileage seemed to change. In other words, I went a lot longer than 10K sometimes. He told me that the oil level sensor in the pan was also a probe that measured the oil life its self.
He had heard that it measured the conductivity of the oil, and as carbon and other things built up, it adjusted the change interval accordingly.
I expressed doubt loudly.
We checked the time left before service. I want to say it was about 2K. I watched while he pumped about two quarts of oil out of the dipstick hole.
Refilled it with the regular synthetic he usually put in my car.
I drove it off, and within about 30 minutes, the oil life had jumped to around 4K.
Convinced me.
It would not go back to 10K after an oil change though. You had to reset it. Not sure how many miles it would add when fresh oil was added.
No idea if newer ones do that, of if anyone else does it. I do know that they had some problems with that probe. It would occasionally start showing low oil when it was not low. And was not an easy replacement. Not sure how it worked, but it would not just report low oil, it would actually tell you how low it was withing a half liter. Or quart, don't remember right now.
Mine started showing low oil, but cleared up after an oil change and I did not have to have the pan pulled to replace it.
Edit:
Just went on Rockauto. That sensor is $172, and is very strange looking. No telling what the heck it does.
