Sounds like the pump is leaking and allowing motor oil to get into your SLS fluid. There is a guy named George Murphy or Performance Analysis that sells a seal kit for the SLS pump, here is his info.
George Murphy
Performance Analysis Co.
969 Oak Ridge Turnpike, Suite 258
Oak Ridge, TN 37830
865-482-9175 9 am to 5 pm ET M-F

He sells a bunch of MB stuff. He has a SLS seal kit for about $40. Give him a call he has a cataloge he will send you for free. The SLS kit comes with instructions.

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