I have seen all sorts of stuff dumped through them strokes.

Local fellow used to burn filtered waste oil mixed with a little bit of gasoline to thin it out.
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Engine oil
Tranny oil
Hydraulic oil
You name it and he fed it to the poor Power stroke.

The little beast always seemed to digest it OK

The 6.5 with the electronic pumps really does not do well with the "alternative fuels"

They will run the Bio/ULSD blends ok but the tranny oils and such are just not going to work well.

Yes, the optical sensor is going to be an issue.

Missy