Ducati Monster 821 Owner's Manual page 225

VISCOSITY
SAE 15W-50
The other viscosity grades specified in the table can
be used where the average ambient temperatures
are within the limits shown.
224
10W
20W
20
30
20W–40 20W–50
15W–40 15W–50
10W–40
10W–30
–10 0 10
40
20 30 40 C
Fig. 160