It is the first time the Volts have won four consecutive one-day games during a season.
And the tense three-wicket win against Auckland in Lincoln has seen Otago's odds of making the playoffs firm considerably.
The Volts (22 points) are in second place, with an eight-point buffer to Northern Districts (14 points) in third place.
Wellington (23 points) is in pole position. Auckland (12 points), Central Districts (11 points) and Canterbury (nine points) fill the bottom three spots.
Not many would have picked the Volts to be so far up the standings. The team has endured lean times and did not start the summer well, with back-to-back losses in the Plunket Shield.
But the Volts are a much better one-day unit, and seized control of the game with a solid bowling effort.
Fast bowler Warren Barnes made an impact in his return to the side with two for 37 from 10 overs, and legspinner Michael Rippon's three for 47 helped restrict Auckland to an under-par 250 for nine.
Otago appeared to have the chase in hand, but the run out of Neil Broom for 49 left the game in the balance.
The Volts needed 94 runs off the last 15, and Nathan Smith helped edge his side closer to the target with a career-high 43 from 45 deliveries.
The 20-year-old had been promoted in the order, and validated the decision with a mature stint at the crease.
Josh Finnie came in to close the innings and clubbed 23, while Rippon held his nerve with an unbeaten 38 at the other end.
Jacob Duffy stroked a boundary through cover to seal the win.
''It is amazing how the margins in sport can be so small,'' Otago coach Rob Walter said when asked how he was feeling about the winning streak.
''Sometimes the changes you make are so small and minor and then the next thing you've won four in a row and five in the season.
''It is great to win but for me ... the real goals for a coach [are] watching young guys perform and deliver for the team. That's the greater satisfaction because you've been part of that journey.''
Otago made a decent start with early wickets. Barnes got rid of the dangerous Sean Solia with an accurate bouncer which hooped off the batsman's gloves.
But the ball which bowled Michael Barry made for even better viewing. It was a terrific yorker which knocked the off stump out of the ground.
Rippon took care of the middle order with some fine slow bowling.
He had his figures damaged somewhat at the end by the Mitchell McClenaghan, who swatted three consecutive fours.
But Rippon had been frugal until that point, and picked up the key wicket of Craig Cachopa.
The Auckland captain held the innings together with a fine counterattack. He towed the Aces through to 166 before he was trapped in front trying to play a reverse sweep for 84.
Danru Ferns whacked a valuable undefeated 35 from 32 balls, and Otago could have done without McClenaghan's innings of 22.
-Wellington's Andrew Fletcher has made a tremendous start to his career. The 25-year-old right-hander scored his third one-day century this season to led his side to a 58-run win against Central Districts in Lincoln.
Wellington posted 266 for eight and reduced Central to 87 for seven. Ryan McCone (52) and Ben Wheeler (56) staged a revival with a 105-run partnership to help Central reach 208.
-At Hagley Oval, Canterbury smashed 307 for four, with Jack Boyle (126) and Stephen Murdoch (112) scoring hundreds.
The pair eclipsed the previous highest second-wicket partnership for Canterbury against Northern Districts, of 189, with a 200-run stand.
It was Boyle's maiden one-day hundred, but Northern overhauled the target with four wickets and 10 balls to spare.
Joe Carter (65 not out) and Peter Bocock (57 not out) put on an unbroken stand of 107 to clinch victory.
