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2002 Mercedes ML320, 132k
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266 Posts
Discussion Starter #1
I realize the FSS determines the oil change interval based on usage. But in 10 years/130k it's been very close to 10k intervals, and it usually counts down. Recently it said 1000 miles to go, and my wife took it on an 800 mile, mostly highway, trip. Came home reading 1100 miles to go. Since then it's counted down to 900, pretty consistent with use. Can the long drive really filter the oil or something to extend the interval that much?

With the college return trip in 2 weeks, I'll probably do the service this weekend anyway. But it's an interesting behavior.
 

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'05 ML350SE
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1,395 Posts
As part of its algorithm, the FSS uses data from a sensor in the oil which measures conductivity, the idea being that a higher conductivity indicates more contaminants.
If sustained high speed driving drives off compounds resulting in a lowering of the conductivity then that would be reflected in the FSS reading. The same with adding fresh oiil which would dilute the contaminants. As an aside, the early MYs had a conductivity sensor in the tranny sump but it was never put to use.
 
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