Factory driver Preining won twice in Porsche's first season in the DTM last year with two-time Le Mans 24 Hours winner Timo Bernhard's operation, following up the Weissach marque's first series victory at the Norisring with a charging drive at a wet Red Bull Ring, while Porsche-contracted Olsen dominated from pole for SSR Performance at Spa.
Preining's move to join the incoming Manthey effort was predicted by Motorsport.com last month and, with SSR switching to Lamborghini, announcing factory drivers Mirko Bortolotti and Franck Perera as part of its three-car roster on Thursday, Olsen has moved across to join him at Manthey following the conclusion of its works involvement with Porsche in the World Endurance Championship's now-defunct GTE Pro class.
Preining said: "The crew is highly professional and the chemistry is right. We are all very motivated. "I'm looking forward to the season with confidence and can't wait for it to finally start."
Olsen added: "I've already worked with the team and I know how well things work at Manthey. This is topped off by the new generation Porsche 911 GT3 R.
"For me this is exactly the right starting point to race at the highest level in the DTM."
Bernhard, meanwhile, will run Asian Le Mans Series champion Ayhancan Guven and German Carrera Cup champion Laurin Henrich in its two cars.
Two-time French Carrera Cup champion Guven finished second in the ADAC GT Masters standings with Porsche outfit Joos Sportwagentechnik last year and also made a strong impression on his DTM debut at the Norisring with the Red Bull Ferrari team by qualifying third for his debut.
"Joining the DTM grid is a huge moment for my career and something I was dreaming for a long time," said the Turkish driver.
"We all know how tight and difficult the current DTM grid is so it will not be an easy season for anyone but, with experience from the team, we will try to put right steps together."
Henrich, a former Porsche junior, is now a Porsche contracted driver with the same status as Olsen.
Toksport WRT was also revealed as a Porsche entrant for 2023 when the series now run by the ADAC - following its sale by Gerhard Berger's ITR organisation - revealed its 13 participating teams on Wednesday but has yet to announce any drivers.
Manthey returns to the DTM for the first time since it ran Mercedes in 2002, an involvement capped by winning the last two rounds of the 2001 season with Patrick Huisman and Bernd Maylander at Hockenheim.
Team founder Olaf Manthey also has a long history in the DTM, having finished second in the inaugural championship in 1984 and repeated the feat in 1985.
Manthey Racing's tie-up with Australian outfit EMA Motorsport continues a burgeoning partnership that yielded second spot at the Bathurst 12 Hour earlier this month, with Preining part of its driver line-up.
The two organisations previously collaborated on an entry to the Spa 24 Hours last year as well as in a round of the Nordschleife-based Nurburgring Endurance Series.
