We've got a 4h 45m layover from a s/h DY arrival at OSL to a l/h DY departure. All one reservation so we should be checked in and our bags will be checked. We're arriving from a Schengen destination, so no immigration. It looks to me that this should be long enough to take the Flytoget to Oslo central station, have lunch and get back to the airport. Would anyone disagree?

Our departure is on DY7001 to JFK at 6.05pm on a Saturday towards the end of this month. What time should we aim to be at the airport by to clear security in time?

Many thanks!