Conor McAleny scored a hat-trick as Oxford's pursuit of a play-off place gathered momentum with a 4-0 mauling of relegation strugglers Chesterfield.
Rob Hall put Oxford in front before McAleny made it two in the 36th minute and then punished some woeful Chesterfield defending in a one-sided second half at the Proact Stadium.
Oxford began confidently and McAleny wasted two chances inside a minute from 12 yards before the visitors went ahead in the 17th minute.
Toni Martinez got behind Chesterfield on the left and pulled the back to Hall who held off a defender before slotting the ball in from close range.
Chesterfield responded with Sylvan Ebanks-Blake releasing Kristian Dennis whose 20-yard shot was beaten away by Simon Eastwood, but Oxford scored again nine minutes before the interval.
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Hall pounced on a loose clearance and set up McAleny who sent a swerving shot from the edge of the box past Thorsten Stuckmann.
Stuckmann kept Chesterfield in the game by keeping out a Phil Edwards header in the 47th minute but he was beaten again just after the hour mark as Oxford moved further ahead.
McAleny was allowed to run inside unchecked before firing a 25-yard shot inside Stuckmann's right post as it became 3-0.
Chesterfield fell apart in the 69th minute when Ian Evatt gave the ball away and McAleny scored his third from just inside the area as Oxford cruised to victory.