ΔE 15.2, loose: different enough that you should pick on purpose. Oily Steel is a little darker, more muted than Gunmetal Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Oily Steel is a little darker, more muted than Gunmetal Blue.
The same difference applies the other way round: Gunmetal Blue is a little lighter, more saturated.
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 Gunmetal Blue on the colour wheel See Oily Steel on the colour wheel
All matches: Gunmetal Blue equivalents · Oily Steel equivalents