I recently installed two new pumps on my mower. as far as oil is concerned, I went to the convenience store and purchased the least expensive 20w50 I could find.
when I do my next change, what oil should I get, or does it not matter when useing in hydro system.
No manufacturer I'm aware of recommends dino auto motor oil for their hydro units. Most recommend full synthetic 20W50 motor oil. Most commonly Mobile 1 but there are some others that are acceptable.
Best bet would be to check the owners manual for the machine and see what they recommend. You can also look up the Skag website and check for the owners manuals there.
For some reason, no manufacturer ever recommends an oil that is inexpensive. Many oils are compatible with seals and other parts but they want owners to buy the most expensive for some reason. I found that out when I put hydro oil in my JD 425.
