Johnston came home in second place, to give himself a mathematical chance of winning the championship.
Neilson finished 11th, but Sandy Flett was taken to the wall by Dennis Black in the 82V car. That's where his night and title chances ended.
The second stockcar race was full of drama.
Mooney was driven hard into the wall on the back straight, puncturing his right front tyre.
He continued to circulate, while fending off several attacks.
Black was hitting anything that moved, as were Francis Potaka (52V) and Ken Meehan (27P).
When the flag fell, Luke Miers (15P) won with Blair Lockett (89V) second and Johnston third. Neilson was seventh, while Mooney's 2NZ car limped home in 14th place, four laps down.
Yet completing the race was enough to give Mooney the $2300 winner's purse with 215 points over the four meetings.
Johnston finished second on 201 points, with Neilson third on 182 - an excellent result for his first year in the Stockcar class.
Dylan Smith (53V) took a clean sweep of the Youth Ministocks points titles.
Smith's good luck was at Trazarn Ryland-Annabel's expense, however, as the driver of the 5V car was ahead of Smith in the feature when he got caught up with a slower car and went nose-first into the wall on the front straight.
Ayrton Smith (64P) won both Adult Ministock points titles.
His main rival, Brandon Jurgeliet, turned up in a borrowed car, having sold the 48P machine during the week, and was unable to overpower Smith.
John Caird (53V) won the season-long points title over Jason Pointon (71V).
Pointon had enough of a Feature Points buffer, however, to survive a DNF after a heavy collision with the wall left his car's right front suspension looking very second-hand.
And in the sidecars, nothing went right for local crew of Aaron Rose and Amelia Stanley (34V) as their season-long rivals Mitch Byers and Tony Hislop (17P) clinched the points win.
The focus on Sunday was on fun, with women's, novice and crew racing before the season ended on a smashing note.
Thirty cars of all shapes and sizes rolled out of the pits for the Demolition Derby.
Many cars were carrying tributes to Palmerston North Stockcar and Derby competitor Brent Lowe who was killed on Christmas Eve.
Vehicles ranged from Japanese compacts to the Wolseley of Allan Lowe, but not many were unrecognisable by the end of the derby, and few were roadworthy.
As the damage count grew and the laps ticked over, two cars were left.
The red 61 car of Nathan Palmer had stayed out of trouble for most of the race, while Eugene Robbemond, taking a break from photographing the action, battled on in the damaged No33 car.
The two survivors came together on the back straight, and it was Robbemond's car that spluttered away from the confrontation, still mobile - just. However, the officials deemed otherwise, and Palmer was awarded the victory in somewhat controversial circumstances. Robbemond was certainly the crowd favourite in the latter stages.
The closing of the season also marked the end of an era.
Long-time Wanganui Stockcar and Speedway Club president Alan Luoni is standing down after many years of service to the club.
He has been a larger than life figure at Oceanview who has worked tirelessly for the sport.
Luoni will not be lost to speedway, however.
He is seeking election as a director of Speedway New Zealand.
The club wishes him well in this venture, and thanks him sincerely for everything he has done to promote the sport and the club, which he leaves in great heart.
For now, however, it's time for everyone to recharge the batteries, and for competitors to burn the midnight oil repairing or replacing their machinery.
The 2016-17 season starts in October, and will be highlighted by the New Zealand Sidecar Championships.
