Just picked up the February issue of Road & Track magazine.
On page 141 ( Technical section ), a reader is questioning extended oilchange intervals.
R & T's response ( in my humble opinion ) is right on the money !

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2007 C 230 Sport.

What was the response?

My subscription ran out 8 years ago.

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'90 300SE 298k
-300K and it gets put into retirement.
'80 300D 255k Purchased new by family in 1980.

Had a:
1973 220 (gas)
1980 300SD
1992 400E

They basically say to stick with the mfg's. recommendation.
Also, and very important, is your kind of driving-cycles.
I.e. short trips, cold weather, hot weather, dusty conditions, etc.,play a big role in the equation.
They also stress the importance of well-filtered air ( to eliminate dirt contamination of the oil ).
You'll just have to go to the local Supermarket, read the article............and then place the magazine back on the shelf.

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2007 C 230 Sport.

So, basically they haven't changed their opinion since the magazine was founded . . .

More important than the interval is using full syntheic oil especially during the winter. Syntheic oil is the only snake oil proved to actually work as advertised. I change my 300TD oil every 5,000 miles using good German filters and the syn oil.

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Bill Reimels
Now down to one:
1972 300SE 3.5 W109 (Euro delivery)