Chasing a modest 207 for victory, Oman huffed and puffed to victory, scoring 207 for six in 47.4 overs, thanks to a crucial unbroken seventh-wicket stand of 71 runs between Suraj Kumar (35 not out) and Mohammad Nadeem (29 not out) after in-form Aqib Ilyas had struck a valuable half-century (63).
Duleep Mendis-coached Oman ended the tri-series with three wins for six points from four matches, its lone defeat was against the hosts on Sunday.
Scotland topped the table on better net run-rate (NRR) as it too had six points. While Scotland had a NRR of +0.556, Oman had -0.234. PNG lost all the four games it played.
On Wednesday, Oman lost its opener and vice-captain Jatinder Singh early (12 for one) but a 98-run second-wicket stand between Khawar Ali (32) and Ilyas rebuilt Team Red's innings before a middle-order collapse put it on backfoot.
Ilyas' exit at 110 for two in the 23rd over triggered the mini-debacle as Oman was down to 119 for four after 27th over and appeared in trouble with the scoreboard at 136 for six in the 33rd over. Ilyas' knock off 76 balls was studded with six boundaries.
Following Ilyas in the pavilion were skipper Zeeshan Maqsood (4), Ali (32 off 67), Ajay Lalcheta (12) and Sandeep Goud (0).
Allrounder Nadeem and wicketkeeper-batsman Kumar then batted sensibly as they shepherded the innings to steer Oman home in the 48th over.
Kumar was the more aggressive during the stand as he hit five boundaries in his 46-ball knock while Nadeem had just one four in his 54-ball innings.
Charles Amini was the most successful PNG bowler with three for 39.
Earlier, PNG was in trouble after a 48-run opening partnership between Tony Ura (34) and Gaudi Toka (23), as it slumped to 106 for six in 23 overs. A 52-run stand between Chad Soper (29) and Kiplin Doriga (24) resurrected the PNG innings before Hiri Hiri's unbeaten 31 off 33 got the team to a modest 206 for nine.
Jay Odedra was the pick of Oman bowlers as he grabbed four for 34. Bilal Khan took two for 32 while Maqsood, Ilyas and Ali bagged a wicket apiece.