  We present the XMM-Newton X-ray eclipse lightcurve of the dwarf nova OY Car.
The eclipse ingress and egress are well resolved for the first time in any
dwarf nova placing strong constraints on the size and location of the X-ray
emitting region. We find good fits to a simple linear eclipse model, giving
ingress/egress durations of 30+/-3 sec. Remarkably this is shorter than the
ingress/egress duration of the sharp eclipse in the optical as measured by Wood
et al. (1989) and ascribed to the white dwarf (43+/-2 sec). We also find that
the X-ray eclipse is narrower than the optical eclipse by 14+/-2 sec, which is
precisely the difference required to align the second and third contact points
of the X-ray and optical eclipses. We discuss these results and conclude that
X-ray emission in OY Car most likely arises from the polar regions of the white
dwarf.
  Our data were originally reported by Ramsay et al (2001), but they did not
make a quantitative measurement of eclipse parameters. We have also corrected
important timing anomalies present in the data available at that time.
