As I recall I read somewhere, that there are several sensors in MB engines to monitor engine oil quality. So after an oil change, why FSS won't be able to tell the oil is good for another 10000 miles and still count down based on the original pace?

There is only one sensor, it's called the oil level/quality sensor.
The countdown is based on an algorithm which reads in info such as time units, miles spent at lower speeds, miles spent at higher speeds, miles spent at idle, etc to calculate the proper time to have the service done. I believe in the US it always starts at 10,000 miles and 2 years. It also looks at the oil quality, both the initial reading (which is a reflection on how good the oil is when new, dino vs synthetic, etc) and also a running calculation on the contamination factor of the oil through it's life by measuring it's capacitance, which also will change the time/distance remaining to the next service.

Gilly

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Here's the datasheet (pdf)

http://www.temic.com/e/prod/sensor/pdf/qlt.pdf

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W163.154, M112.942, 722.662, ZF.970.402

That doesn't look alot like what's in the 112/113 motors. I believe that probably does serve the same function, I believe it is made by Temic. At any rate, that, in effect is what it is. It's only a single component, not several different sensors, maybe I'm not communicating this very well. It does have 3 different functions, I only gave it credit for 2 functions; oil level and oil quality. It also measures the oil temperature. Wish I knew how they calculate oil level based on capacitance. Hmmmmm.

Gilly

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Gilly,

true it looks a bit different in 112/113s, but you are correct anyways, it's all in one. How they do the level measurement? Remember it uses two capacitors and one gets the dielectric constant, between the quality and common electrode. Then it reads the capacitance of the second, between level and common electrodes and since the capacitance depends on the dielectric of the medium, oil or air in this case, one can calculate the fraction of the level electrode covered by oil and thus obtain the level.

Delphi also developed an oil level meter, about 2 years later, and put a nice writeup on the net, including a graph showing level readings of 5 different oils (Figure 2).

http://www.delphi.com/pdf/techpapers/2000-01-1366.pdf

PS. The temperature sensor in the QLT is a PT1000 from Heraeus GmbH (the best, very precise) as far as I know.

Enjoy,

Wolfgang

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Thanks for the information, but my realy question is why FSS can not reset itself after a fresh oil change? It should find out that the oil quality has changed so much that it should be good for another 10,000 miles. ANyway, I was just confused when I did an oil change on my ML with 3500 miles. I checked FSS and it indicated exactly the same number of miles before and after the oil change. And after driving a tank long, the FSS continued to decrease the number (7000->6700 or so).

Even though the oil/filter are fresh, the other filters still need changing. The FSS will reset to a degree by changing the oil, but if the interval between filter changes has expired it will no longer extend itself.

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'00 ML320 "Casper"
'92 400E "Stella"

I don't think it calculates the oil level based on capacitance otherwise it won't warn that the level is only accurate when vehicle is level. I believe the sensor integrates the level function just like any simple level measuring switch. It's the quality that's more tricky. Temp. is also very easy to measure.

You're missing a big point here. The FSS is a Flexible SERVICE System. It's not only a oil change indicator system. So, simply changing the oil will not reset the FSS automatically to 10K. It will change the service interval some (it'll sence new oil and react). However, since FSS calls are not only for oil changes, it will not reset to 10K. As a matter of fact, the system very conservative and is designed to be set manually, that way all sub systems requiring a FSS service call are attended to. So even if you attend to all FSS sub-system calls, the system will not reset itself until you manually reset it.

Now I think it makes sense. Through reading the manual, I found there should be an A service either FSS thinks so or every 12 months. So if my truck is only 8000 miles on the meter, but already bought for a year, should I call the dealer to schedule an appointment or, would the dealer even do it since FSS says there is still 3500 miles to go.

with 3500 miles to go, i doubt the dealer will do it. Usually, they don't mind 1000 miles to go. Ask anyway. In anycase, if you dont do it, the FSS system will revert to a B service based on time instead of mileage, then you'll have to take it in.

Wow, lots of FSS questions lately.
The system base setting in a US version is initially set at 10,000 miles or 2 years. I don't believe it will recommend a "B" service based on over-running the time element, only the 14,000 miles.
IMO it may be possible to ask the dealer to do the service, even based on the miles remaining. If you mention it's been a year since you bought it, they may see the wisdom of performing the service.

I think the reset procedure exists just so that this system will start over at the 10,000 mile base point. The system will then accept the current quality readings as a base point for the initial quality of the oil. I believe it will begin modifying the algorithm almost immediately based on the quality of the oil that was put in. Resetting will also immediately reset the time interval too.

Gilly

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Just for an update. I talked with my dealership and the service advisor said they don't go with the time as MB only cares FSS. They wouldn't do an A service if FSS indicates more than 1500 miles left.

Thanks all for those informational postings!

Anyone know Exactly what they do doing FSS A or FFS B? what procedures are they SUPPOSE to do?

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