Gravely Commercial 60 inch cut I use at work with a 29 hp Kohler Command Pro EFI. I change the oil every 50 hrs, as I always run it full throttle cutting levees, its always on an incline, severe service. I recently used Valvoline VR1 20W50 racing oil (black bottle) for the last oil change with a Napa Gold filter. Should the black or silver bottle VR1 be ok for 50 hr intervals? This particular oil is blue in color. The engine specs 10W30, but I've been running 15W40 and 20W50 with no problems. its a 2013 year model and has right at 1,087 hrs.
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