Oil quality is a major contributor to your engine's performance and life. Always select good quality engine oil. Suzuki recommends the use of suzuki performance 4 motor oil or equivalent engine oil. Use sf/sg or sh/ sj with jaso ma in api (american petroleum institute) classification.

Api: american petroleum institute jaso: japanese automobile standards organization
Sae engine 011 viscosity
Suzuki recommends the use of sae 1 ow-40 engine oil. If sae 10w-40 engine oil is not available, select an alternative according to the following chart.

Jaso T903
The jaso t903 standard is an index to select engine oils for 4- stroke motorcycle and atv engines. Motorcycle and atv engines lubricate clutch and transmission gears with engine oil. Jaso t903 specifies performance requ irements for motorcycle and atv clutches and transmission.
There are two classes, ma and mb. The oil container has following classification for confirming the standard.

Energy conserving
Suzuki does not recommend the use of "energy conserving" oi ls. Some engine oils which is api sh or greater has "energy conserving" indication in api classification doughnut mark.
These oils can affect engine life and clutch performance.
Fuel
Engine coolant solutionLeft handlebar
Clutch lever 1
The clutch lever is used for disengaging
the drive to the rear wheel
when starting the engine or shifting
the transmission gear.
Squeezing the lever disengages
the clutch.
Headlight flasher switch 2
Press the switch to light the headlight.
Dimmer switch 3
" " ...
Exhaust control system construction
Excv cable no. 1 (Cl)
Excv cable no. 2 (Op)
When
loosening or tightening the pulley bolt, be sure to fix the
pulley with an adjustable wrench, or excva may get damaged.
5 N·m (0.5 Kgf-m, 3.5 Lbf-ft)
42 – 43 Mm (1.65 – 1.69 In)
60 – 61 Mm (2.36 – ...
Oil cooler / oil cooler hose inspection and
cleaning
Refer to “exterior parts removal and installation” in section 9d .
Oil cooler hose inspection
Inspect the oil cooler hoses for any damage and oil
leakage. If any defects are found, replace the oil cooler
hose with a new one.
Oil cooler inspection
Remove the oil cooler guard (1).
...