I would suspect an injector. I don't work on farm equipment, but if it were a road tractor, that's what it would be. We often add some fluorescent dye (like some a/c oil w/ dye) to the fuel filter, and run it with the valve cover off while shining a UV light on it. You should be able to see with one is leaking fuel into the oil.
8 qt>
if it si 15w40 engine oil
@ 5 gallons with Wix oil filter 57243
The 317 john deere does not have an oil filter.
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This is the oil filter that John Deere uses on all Kawasaki Motors that are used in John Deere equipment.
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A John Deere model A holds 9.25 qts of oil.
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The oil capacity of a John Deere 2020 is about 7 quarts.
John deere part M806418, or I prefer the Mobil m1-110. The Mobile has the same interface at the screw on but is a little taller. Works fine and has a more filter element.