Recipe of the day: DIYSwede's microbrewed ISO 68-ish Way Oil

[mklotz]

AFAIK, any light machine oil could be used, not only of ISO 32 grade - you just have to alter the proportions accordingly.
If you borrow Marv's excellent formula from the post above, for instance:
32 * R + 125 * (1 - R) = 68,
and just swap the first "32" therein for the viscosity of your chosen oil, I'd guess you'd be alright.

It might help if I generalize the equation and show how to solve it.

A*R + B*(1 - R) = 68

where A and B are constants representing the viscosities of the two oils being mixed.

A*R + B - B*R = 68

R*(A - B) = 68 - B

R*(B - A) = B - 68

R = (B - 68) / (B - A)

As a check, plug in the values of A (32) and B (125) from the original problem...

R = (125 - 68) / (125 - 32) = 57 / 93 = 0.619 = 62%