Do you need to use each type of specified oil in the owner's manual or can you use one oil for all required implements. I have a RC2060 rotary cutter and a JD 655 tiller. Each one specifies a different oil to use in the gear box. GFP only carries the GL-5 for the tiller. The owner's manual for the RC2060 says I should use EP80-90W. What are most people doing and by most I mean everyone on here. Thanks in advance.