The 27-year-old went unbeaten as some of the world’s best riders put on a night of superb entertainment in front of a socially distanced crowd.
Australia’s Chris Holder – the 2012 world champion – joined Danish favourite Nicolai Klindt on the podium.
Britain’s Dan Bewley finished fourth after a run-off with Rasmus Jensen, and those four riders now go through to the Grand Prix Challenge later this year, for the chance to make the Grand Prix series in 2022.
Musielak – who was mobbed by Polish fans after his victory – said: “I was pretty fast tonight – it was a great night for me.
“I enjoyed the track – it was a great racetrack. The track and the stadium are beautiful, and it would be great if the Grand Prix would come over here, because the racetrack is just awesome.
“I have to slow down and enjoy the moment, this night, but I have a big challenge in front of me now.”
Klindt also sang the praises of the circuit and the set-up at Ashfield.
He said: “I’ve said before that it’s the best club in Britain.
“Everything throughout the day, it’s been superb, and I know it’s probably a big ask but I would love to see a GP here in the future.”
Holder, who is aiming to return to the world stage after a few years out, said: “The track was prepared so well – a little bit slick, but it’s safe, and you can go everywhere. The inside was working really good, and the outside was working and both had their pros and cons.
“Glasgow in the past has been a bit tricky but the track tonight was great. Credit to the club, during lockdown they’ve obviously put in a bunch of work and it showed tonight with the racing.”
Glasgow’s own Broc Nicol struggled to make an impact, scoring just three points in tough company, while Brits Charles Wright and Lewis Kerr scored seven and six respectively.