ΔE 15.9, loose: different enough that you should pick on purpose. Middle Stone is much more muted, cooler than Petroleum Brown.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Middle Stone is much more muted, cooler than Petroleum Brown.
The same difference applies the other way round: Petroleum Brown is much more saturated, warmer.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Petroleum Brown on the colour wheel See Middle Stone on the colour wheel
All matches: Petroleum Brown equivalents · Middle Stone equivalents