...What kind of oil does everyone use in their bike? 10w-40 seems common.
So I don't get into a big oil debate, here's what the owner's manual recommends;
Recommended Engine Oil
Type: API SE, SF or SG
API SH, SJ or SL with JASO MA
Viscosity: SAE 10W - 40
Capacity: 1.3 L (1.4 US qt) (When filter is not removed)
1.6 L (1.7 US qt) (When filter is removed)
○Although 10W-40 engine oil is the recommended oil
for most conditions, the oil viscosity may need to be
changed to accommodate atmospheric conditions in
your riding area.
What is also listed in a chart is 10w-30,10w-50, 20w-40 & 20w-50
What it does not list is 15w, which falls in between 10w & 20w
There are also alternative oils that meet the type requirement recommended by Kawasaki and recommended by many in the motorcycle community.
These are formulated so close to motorcycle oil that they meet the JASO certification requirement.
1. Castrol RX Super 15w40
2. Chevron Delo 400 15w40
3. Mobil Delvac 1300 Super 15w40
4. Pennzoil Long-Life 15w40
5. Quaker State 4X4 Synthetic Blend 15w40
6. Shell Rotella-T6 15w40 (favorite among other motorcyclist who change oil frequently)
7. SuperTech 2000 (WalMart) 15w40
8. Valvoline All Fleet 15w40
9. Castrol Syntec Blend Truck and 4X4 15w40
You will be fine with 10w-40 if it is in the temp range you ride in. From what I've read, regular 10w-40 can shear down to 10w-30 in a short time while synthetics last longer.
As for me I ride longer distances at higher speeds more than the average rider. I'm also a little heavier too, so I use CASTROL Act>evo Semi-Synthetic 4-Stroke Motor Oil 20w 50 and change it frequently. Why? because the book says I can. Besides, it makes the bike ride smoother. Keep in mind the Ninja 250 is a high revving bike and any oil you put in it will breakdown. How fast, depends on your driving conditions.
Everybody has their own choice and reason for what they use. Kawasaki gave us very good options, that they know the bike can handle.