Changing oil but not filter - different viscocities

[Human Potato]

Hi Guys,

I want to change from 10W40 to 20W50 without replacing the filter.  I know that this will result in a little contamination of the oil but the old oil is pretty clean anyway.  Is there anything I should know about before doing this, or will it simply result in the new thicker oil being very slightly diluted?

The reason I am doing this is to try to stop a noise from the engine that sounds a little like the wind whistling thru your helmet but a little lower in pitch.  The noise occurs only at 4,500 RPM and I have found that it is less noticeable when the engine is cold (oil thicker?).  Seeing as the manual says I can use 20W50 in my temperature range I figured it would be no harm in trying.

It is a GSX 650F engine (same as the smaller bandit) and I think it is some kind of resonance occurring within the engine at that specific vibration and I am hoping that the thicker oil will dampen the vibration slightly or something.  Any ideas about this?

[Dink_1170]

Absolutely no reason not too.

Dink

[pmackie]

You'll be fine as far as "blending" the two oils go. Ideally, you will use the same brand/oil line to minimize additive differences, but even that is not a big deal.

As for it actually reducing or eliminating the 4500-5500 rpm "600 bandit buzz", I doubt it will have much effect, but it won't hurt to try.