Just some FYI for you, if anyone is giving you the dire information of "you need to replace your engine" based on the same limited information you provided here then the source of that information should be thoroughly suspect. While I concede that an engine requiring the addition of "some oil" at given mileage intervals is not a good sign it does not immediately point to massive engine failure. Especially when you seem to indicate that in the past there were oil trails left on your driveway that would typically point to some sort of seal leak.
As far as an engine drinking oil being a common Nissan problem, more likely it is a problem with any vehicle that has not been properly maintained. You don't mention if you bought the vehicle new or used or know it's past service history. If you are adding oil ever 4000km at what point are you actually changing the oil?
Back to your problem, if I was you the first step you should be doing is get the engine scanned and find out what codes are being tripped to turn the engine light on. Then go from there with that information.