  We present a comparative study of X-ray emission from a sample of active M
dwarfs with spectral types \hbox{M3.5 - M4.5} using XMM-Newton observations of
two single stars, AD Leonis and EV Lacertae, and two unresolved binary systems,
AT Microscopii and EQ Pegasi. The light curves reveal frequent flaring during
all four observations. We perform a uniform spectral analysis and determine
plasma temperatures, abundances and emission measures in different states of
activity. Applying multi-temperature models with variable abundances separately
to data obtained with the EPIC and RGS detectors we are able to investigate the
consistency of the results obtained by the different instruments onboard
XMM-Newton. We find that the X-ray properties of the sample M dwarfs are very
similar, with the coronal abundances of all sample stars following a trend of
increasing abundance with increasing first ionization potential, the inverse
FIP effect. The overall metallicities are below solar photospheric ones but
appear consistent with the measured photospheric abundances of M dwarfs like
these. A significant increase in the prominence of the hotter plasma components
is observed during flares while the cool plasma component is only marginally
affected by flaring, pointing to different coronal structures. AT Mic, probably
a young pre-main-sequence system, has the highest X-ray luminosity and exhibits
also the hottest corona. While results of EQ Peg and EV Lac are presented here
for the first time, AT Mic and AD Leo have been investigated before with
different analysis approaches, allowing a comparison of the results.
