Yamaha RHINO YXR660FW Owner's Manual page 278

Recommended engine oil:
See page 10-2.
Oil quantity:
Without oil filter cartridge replacement:
1.90 L (1.67 Imp qt, 2.01 US qt)
With oil filter cartridge replacement:
2.00 L (1.76 Imp qt, 2.11 US qt)
CAUTION:
_
G
In order to prevent clutch slippage (since
the engine oil also lubricates the clutch),
do not mix any chemical additives. Do not
use oils with a diesel specification of "CD"
or oils of a higher quality than specified. In
addition, do not use oils labeled "ENERGY
CONSERVING II" or higher.
G
Make sure that no foreign material enters
the crankcase.
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