Oil oops

[NB250]

Hey,

When I did my oil change before the winter, I put in 10W30 oil because I thought I had read that in the manual. However on the oil cap itself it says 10W40.

What is the difference? And will this harm the bike?

[Easy Rider]

What is the difference? And will this harm the bike?

(Guessing at the climate extremes where you live.......)

No.
Not unless the temp. exceeds 86 F. for very long.
This from the chart in the user's manual.

It will absolutely be OK for spring and early summer.

[jonathan180iq]

Not really much difference, unless you do a lot of long distance/hard riding that might cause your bike to reach a higher temperature than the average GZ.

[primal]

More to the point, did the 10W30 oil have friction modifiers in it? If so, you'll want to drain that oil out and replace it with non-"Energy Conserving" oil. The friction modifiers can cause the clutch to slip.