I just changed the oil this week on my '13 zx14r,
I used Kawasaki conventional 10/40, it seems ok,
but it seemed to drop into gears smoother with
the old oil, and I have no idea what was in it,
when I changed it.
Also, noteworthy to me is that there was/were
6 qts in it lol, I can see why though,
not everyone is aware of how to go about
properly checking the oil level, on this bike
and many others for that matter.

EDIT;
I may be posting this question in the wrong sub
forum, apologies if so. ....

* Last updated by: Stratovarious on 10/18/2025 @ 4:59 PM *

The previous oil might have been a quality synthetic oil like Amsoil. I once used a very expensive Honda synthetic race oil in my Gen1 and the shifting was extremely smooth and quiet for the first couple hundred miles. Other than that, I've used Rotella T6 full synthetic and I don't feel it's any smoother than conventional. It is cheap enough to change every 2500 miles though.

There's probably a great number of oil threads on here. Just use the search function and I'm sure you'll find a lot of recommendations.

I'm still using conventional oil in my 2024. I've always heard it's best to wait a few thousand miles before switching to synthetic. That Honda synthetic I tried was at about 3000 miles and that's also when my head cover gasket started leaking. I'm sure it would have leaked eventually no matter what but the synthetic didn't help.