guessing.....somewhere between 50:1 and 100:1
so reckon on around 75:1 and you are probably near the mark...ish
i have not checked mine so have no clue but it never smokes so i would reckon it uses a lot less than a regular 2 stroke so the figures above could be wrong as well.
now i have the entire stocks of Barrus in my garage i seem to have lost what little urge i had before to track oil consumption!!