  We conducted experimental investigations into the short-term and long-term
impact dynamics of pure water drops on silicone oil-coated surfaces. Our
observations revealed distinct phases: initially, rapid maximal spreading
followed by retraction, subsequent oscillations characterized by a relatively
stable contact angle, and a final phase involved the gradual spreading of the
drop on the underlying solid surface due to the rupturing of the oil layer. The
maximal spreading radius follows $We^{1/4}$ scaling, where $We$ is the Weber
number, independent of the viscosity of the underlying oil layer. By
introducing fluorescent tracer particles in the oil, we noted that the drop
expanded over the oil layer during the initial spreading without displacing
oil. Subsequently, as the oscillations dampen, the drop ruptures the oil layer,
initiating a dewetting process and spreads over the solid surface, leaving a
tiny oil droplet under the water drop. Upon completion of this dewetting
process, the onset time for the drop spreading nonlinearly increased with the
oil layer thickness as $\sim d_o^2$, which we attribute to the dewetting
dynamics. Our findings unveil intriguing dynamics of water drops impacting on
oil-coated surfaces.
