The U's kept their push for promotion well on track with another good away performance to add to their repertoire as goals in each half held Carlisle at arms length.
Oxford settled their promotion jitters early in the piece when they broke at pace from a Carlisle free kick. A nod down from Ellis on the edge of the visiting box evaded Ibehre and a sweeping pass sent Hylton on a run. He went past Grainger and picked out Maguire in the box and an outsretched leg from Ellis was enough to send the forward on a tumble. He quickly dusted himself down and he made no mistake with a confident spot kick.
Away tails were up and they almost struck again when Hylton pulled wide on the right. He stepped inside for the shot but Gillespie was well placed to make the save.
Danger man Hylton clipped a header wide as he found space from a Macdonald cross, and the same player went close again when he sent another header just over the bar.
The Cumbrians took a while to settle but a run from Wyke provided a spark as he burst through three challenges before being hacked to the floor. The free kick from Grainger was well dealt with by the wall.
Blue shirts stayed forward and a half clearance sat nicely for Joyce as he ghosted into space 23-yards out. A precise volley flew through bodies and it bent just past the upright with Buchel at full stretch.
Flowing football put Brough in space as Carlisle upped the pace and his low delivery had Kennedy interested. He put his laces through the shot but Skarz was there to get in the way.
A training ground free kick routine ended with a shot over the target from Joyce, as he and Grainger had a pop, but the home side came knocking again when Ibehre fed Wyke on an overlap with the outside of his boot. His fizzed cross beat the keeper but Wright kept his eye on it and he hooked it away.
Oxford sat deep and struck on the break and the tactic almost paid off when Ruffles spotted O'Dowda in the centre circle. He angled his run at the box but his bullet of a shot somehow edged wide as he went for glory from 18 yards.
More good work from Hylton from a quickly taken throw allowed him to run clear, and he spotted MacDonald with time on his hands. A rasping shot followed but it was always heading high.
An unexpected opening for Maguire punctuated an otherwise slow start to the second half when a clearance from Gillespie rattled into his shin. The ricochet was heading over the line until the keeper recovered and scooped it up.
The Carlisle response was a long ball forward which Ibehre nodded into the mix. Wyke was there but a combination of defender and stopper was enough to direct his shot over the bar.
The hosts went for a quick ball forward again moments later and a lovely touch from Wyke set Stacey for the shot. He kept his head over it and wheeled away in frustration as it shaved the outside of the post.
Wide man Alex Gilliead ran into space as Carlisle started to click and his cut back brought another shot from Stacey. It was a difficult chance and it dropped harmlessly onto the roof of the net.
A dangerous free kick caused problems for United when it pinged around inside the box but Kennedy got a boot in the way before Sercombe could pounce.
Gilliead worked his way through as he exchanged passes with Wyke, in what was a lovely passage of play to watch, and he was left with just the keeper to beat as the final touch took him clean through. Buchel sprinted off his line and he did well to block with his arm.
Carlisle were denied what looked to be a certain penalty when Kenny stopped a Grainger cross with his arm, and the Oxford goal lived a charmed life when the resulting corner was met by a crisp volley from Joyce. Ibehre got a touch as it sped on its way but Kenny was there to swipe it away to safety off the line.
Oxford punished the miss when they burst forward with men to spare and Sercombe was able to pick his spot as he broke through to finish from close range.
A fantastic save from Gillespie - a tip onto the post from Bowery - kept the gap at two goals when Bowery went for a thunderbolt from an angle, and Sercombe scuffed wide from 19 yards when he had more time as the U's relaxed into their lead and maintained their position in the top three.
Oxford - Maguire (4 pen), Sercombe (73)
United - Miller (66)
Oxford - Maguire (18), Wright (82)
Carlisle United - Gillespie, Miller, Ellis, Grainger, McQueen, Joyce, Comley (Stacey 46), Kennedy, Brough (Gilliead 46), Wyke (Asamoah 82), Ibehre. Subs - Hanford, Atkinson, Smith, Sweeney.
Oxford United - Buchel, Skarz (Lundstram 46), Wright, Sercombe, Hylton (Waring 84), MacDonald (Bowery 72), O'Dowda, Kenny, Maguire, Dunkley, Ruffles. Subs - Slocombe, Long, Roberts.
Referee - Mr Philip Gibbs
Attendance - 6,948 (2,283)