Hartlepool twice led through Joe Grey and a wonderful Callum Cooke strike only for Olly Sanderson and Canice Carroll to level things up.
But Carroll’s goal sparked a forgetful seven minutes for Askey’s side as the home team ran away with things with quickfire goals from Josh Ashby and substitute Pierre Fonkeu.
And there was still time for Fonkeu to add his second and Oxford’s fifth of the game when turning in a rebound from Carroll’s header five minutes from time.
It was the first time Hartlepool had ever come up against Oxford City after the Hoops earned promotion from National League South last season.
Usually this would be the kind of fixture you would expect to see in a cup competition but the two sides met as equals at Marsh Lane – although you could even argue that Oxford held a slight advantage given Hartlepool were testing themselves on an artificial pitch for the first time this season.
Askey had voiced his concerns over playing on 3G pitches ahead of the trip to Marston due to potential injuries – Pools having already dealt with two significant injury blows this season due to the National League’s condensed fixture scheduling with Dan Dodds and Anthony Mancini the unfortunate duo.
Pools not only had the artificial pitch to contend with, however, with temperatures soaring ahead of kick-off.
Ross Jenkins’ side had won their first ever National League game last time out on home soil with an impressive 4-0 victory over Boreham Wood with Hartlepool seen, potentially, as an even bigger scalp.
Askey kept faith in the side who beat Wealdstone with goalkeeper Pete Jameson, who impressed on debut in that victory, continuing in goal as well as Brody Paterson’s inclusion at left wing-back, despite Alex Lacey’s return from fitness.
Paterson’s involvement meant captain David Ferguson was kept as a left-sided centre-back, with Lacey back on the bench.
The National League’s player of the month for August, Emmanuel Dieseruvwe, continued to lead the Pools attack with Grey in support while the hosts, significantly, were without leading scorer Josh Parker and defender Andre Burley who were both away on international duty – Parker having scored five times in seven appearances this season, including in his last two.
But any worries of this fixture being a potential banana skin for Hartlepool seemed to be alleviated early as they quickly demonstrated their, assumed, superior quality over a team who were two division below them last season.
Dieseruvwe caused problems for Chris Haigh when meeting Ferguson’s cross from the left as the pair looked to continue their fine bond so far this season.
And it was a cross from the left which gave Charlie Seaman a good opportunity to opening the scoring when he picked up a loose ball in the area after Haigh had flapped at the cross, but the Doncaster Rovers loanee fired over.
Dieseruvwe then glanced wide Luke Hendrie’s cross to the back post as Askey’s side continued their bright start in the blazing hot sunshine.
Cooke was next to test Haigh when he cleverly fired a free kick under the wall but Haigh was equal to things before the home side fashioned their first opening of the game when Tafari Moore found space on the right to pick out Lewis Coyle in the area but the midfielder was off target with his volley.
Hartlepool soon took the lead their early start merited and it, again, came from a deep cross as Hendrie floated a ball to the back post for Dieseruvwe who did well to head back across goal for Grey with the young forward climbing highest to head back across goal and into the corner beyond Haigh.
It was an ideal start for Pools who could dictate the tempo of things and make the home side chase them in the heat before things turned somewhat following a stoppage in play for a drinks break.
Askey was forced into an early change with Kieran Wallace replaced by Oliver Finney which may have upset Hartlepool’s rhythm as Oxford soon levelled through Sanderson.
And it was a goal almost from nothing as a ball down the right was crossed in towards the near post and Sanderson was on hand to turn in.
It was a frustrating setback for Pools who had to start again with Tom Crawford flashing just wide from distance.
But Pools didn’t have long to wait before restoring their lead and what a goal it was as Cooke curled in delightfully from outside the area into the top corner in front of the travelling fans.
Pools had been probing against a compact Oxford, who had everyone behind the ball, without being able to find a killer pass between the lines and the midfielder, from Dieseruvwe’s short pass, struck first time beyond the outstretched Haigh.
The goal appeared to settle Hartlepool and allowed them to control things from the off after the break before the game flipped on its head on the hour in a stunning seven minute period as the hosts scored three times in a remarkable turnaround.
Pools were again undone by a set piece when a low free kick from the left was recycled by Fonkeu who stood a teasing cross up into the box for Carroll to tower a header beyond Jameson before Jenkins’ side took the lead within a minute.
Reece Fleet was able to surge forward following a mistake in defence before his effort fell kindly for Ashby who finished brilliantly when placing first time into the corner.
Hartlepool looked shell-shocked but things would quickly got worse when the impressive Fonkeu extended the Hoops’ lead.
Jake Hastie looked to bring the ball out when finding Dieseruvwe and the striker laid back for Onariase whose untimely slip allowed Fonkeu a clear run on goal and he finished well below Jameson.
Pools were punch-drunk and weary as energy-sapping minutes passed by with very little coming in the way of a response to trouble Haigh.
In fact it was Oxford who might have added to their lead when Fleet fired narrowly over from distance before Ashby brought a smart save from Jameson.
But there was still time for Hartlepool’s day to get even worse as Oxford compounded their misery when Carroll headed Ashby’s free kick towards goal which saw Jameson parry into the path of Fonkeu who turned in on what was a desperate afternoon for Pools who will need a response back on home soil.