Can you mix fully & semi-synthetic oils?

Not for my bus, for my daily - a 2004 Volvo D5 diesel

I have loads of bits of oil knocking about after various oil changes & thought I would put them all together for an oil change.

Is it ok to mix slightly different viscocities (e.g. 5/40 & 10/40) & also fully & semi-synthetic oils together?

Thanks

 

Mixing full and semi isn't the end of the world, but I probably wouldn't mix grades of oil.

 

What @AndyC said, I think. Mixing of grades probably ok for ancient engines like our aircoolers, but not for modern stuff, especially diesels, if you want them to last. I'd buy the right oil.

Chuck the other stuff in your van...

 

...but if you buy a used car & top up the oil, you have no idea what was in there previously & I've not had one blow up on me yet.