I have talked with a few folks about this, as well as read the threads listed above, and similar threads on other sites. Some say they have been doing it for a while with no issues...one or two have had problems.

I spoke with our Cummins rep at work about used hydraulic oil and transmission fluid. His answer was " not a problem ".......as long as you have a non-emissions vehicle.

Another friend of mine who has been a diesel mechanic most of his life told me the hyd fluid and tranny fluid, if properly filtered ( and ran at 25-30% ) should add to the life of the IP and injectors.

Now, feel free everyone, to jump in and kick me in the nuts on my comments above. I AM NOT saying this is or isn't accurate. These are simply opinions of people I know. So take it for what it is worth.

I have about 50 gallons of used hydraulic oil with about 3 gallons of WMO mixed in it. I have been filitering the living chit out of it the past couple weeks. I'm taking the truck on a 1500 mile trip this weekend with the rear tank blended at 25-30%. I'll let you know how it goes.