Mixing synth/semi synth oils ...

[oddnumber]

Hullo folks, I'm after using a heavier oil in my Dragstar, heard it quietens the valve clatter a bit. At the minute I've got 10w40 synth in there. The only 20w50 I can find is semi synth - would there be a problem in mixing the two, especially with them being different weights and grades?

Ta for any advice ... :)

[Simon B]

Always done a complete drain of warm system before putting dif oils in, never mixed two different types and really wouldnt recomend it

[Dougie]

Be warned,20/50 may be too viscous when cold to flow through some oilways,causing serious wear.Use a good 10/40 or 15/40 semi-synth.
I used 20/50 in my GS in the past,didn't seem to do any harm,but it did make the clutch and gearbox a bit stiff.

[oddnumber]

Thanks very much folks.

I'd drain the existing oil out first, but I didn't really want to change the filter because I've not long done it. Not a problem if I have to though.

Dougie - might seem daft but whats the difference between 10w40 and 15w40? Is it to do with the viscosity when hot??

Thanks again for the advice.

[Dougie]

The 15/40 is a bit thicker when cold,but not really enough to make that much of a difference.I've never actually used bike specific oil,just good quality car stuff,but I change it and the filter regularly.But then I'm running something antedeluvian with roller bearings everywhere.........:D

[Borg]

mixing some oils can make it turn to a jelly, Change the filter as well. Its soaked in a different oil.

[J Top]

mixing some oils can make it turn to a jelly, Change the filter as well. Its soaked in a different oil.

.....x2!!!

[Mistress Maker]

some can go almost solid......................dont mix them

[Kylie]

Oil... that reminds me... probably ought to check the old girl has some in at the moment :D

[oddnumber]

Thanks very much folks, the advice is much appreciated.

I knew there was some issue with mixing oils, buggered if I could remember what 'd been told though :o

Reckon I'll just stick with my synth 10w40 then.

[Sir Ewok]

I use straight 50, none of this fancy multigrade stuff.....:unsure:
Some peeps won't even mix BRANDS of oil as they have been know to break down easier.