Alternative fluid for SLS ('82 300TD)

[ROLLGUY]

I will be getting my TD back on the road, and would like to do a complete fluid change on the SLS. Do I really need the special fluid that MB calls for? I would think that the hydraulic system is no different than that of a tractor, and wonder if tractor hydraulic fluid would work? I have a couple gallons of the stuff on hand. The SLS fluid is available from our sponsor, but it will take a couple days to get here, and is expensive. The BIG question(s) is(are): Will standard hydraulic fluid harm the SLS system in any way? Is there any ingredient in the SLS fluid that makes it proprietary that regular hydraulic fluid does not have and/or need? Since these systems are so expensive to maintain and repair, I don't want to save a few dollars now, only to spend many more later. Also, I don't know the health or the lack thereof of the SLS in my car. I bought the car 8 years ago, and am just now getting around to working on it. Thanks, Rich