Viscosity selection for engine burning oil.

[Olas]

If its leaking fix the leak. If its burning look at rings and stem seals.

Ultimately a burner is a burner regardless of viscosity (although some people think Maxlife is the voodoo goodness)

 

[BrocLuno]

Yes you can add the Kreen into existing oil and run it to next change.

More important than basic viscosity on the label is oil formulation. While you are searching for viscosity, try some other oils. Delo 400 15w40 has worked for me in the past to slow oil burning

Next step from there is usually 20W-50 GTX ...