mckvakk

I see OPs trip has already passed. But this thread could be relevant to others, so i'll expand it;

If you manage to catch the local trains (R10 - Drammen, R11 - Skien or L12 - Kongsberg), you can save almost half the ticket price, 101 NOK instead of 190. They run at :03 :13 and :43 most of the day at the time of writing, and take a whooping 4 minutes longer than the express train. The ticket for these trains is also valid for travel within the greater Oslo area for.. i believe 2 hours after activation, which means they can be used for buses and metro in town too.

For a longer layover than OP, these trains would also be covered by an all zones 24h ticket for 237NOK which will take you to and from the airport on the local trains, and also free travel on public transport within the city for, you guessed it, 24 hours.

Both the single ticket and 24h ticket for the local trains can be purchased in either the Ruter section of the NSB app which is the train company, this app also allows you to keep track of train times or delays. or via the Ruterbillett app, or from Narvesen and 7-Eleven in the airport arrivals area by the train station.

Depending on what you want to get done in town i would say 4h45min from within schengen is enough time for a short visit to the city. If you're lucky with the gate and train, you could be in town within the first 45 minutes after landing. From outside schengen, add the passport control time, which can vary with time of day.
If you want to eat some good food there are some new places relatively close to Oslo Central that are supposed to be good. Everything from burger to seafood to steak. Theres's even a few really good ones in the Ø building connected to the station, look for the tourist information and you'll find it.

I you want to go sightseeing instead you could easily see both the opera house and castle within a short time. Start with the Opera, which is right beside Oslo Central train station, head left when you get off the escalator from the tracks. spend 30 minutes here. then either walk, which i recommend if time and weather allows it, this takes 20 minutes of straight walking. Or by taking the metro two stops to Nationaltheateret. From here it's a 2 minute walk up to the castle. This could all be completed within 2 hours time.

For bonus if the weather is nice, get some ice cream or sushi/fast food and sit in the park around the castle like us locals do :-)

To be safe i would be checking the NSB or aiport express app (depending on which one you prefer) from time to time to confirm no train delays, and if not i'd be heading back to the airport when there's 2 hours to your flight at the latest. This allows for a slight train delay, security line, and passport control line if applicable. The passport checks can at times be long ish, especially if there's a few widebodies leaving at the same time.

Also remember that there are some new question procedures for US bound flights, not sure how these work out when you're connecting though. Check with your airline for this.

This might be a bit rambling, but i hope it helps someone connecting in Oslo.