Hi,
The day before yesterday when I was on the way to fastfood restaurant I got a red injection sign on the dash board while I was driving. But yesterday the sign came up irregulary and today didn't come up but once very shortly right before I arrived home. So I checked what's wrong with it and there can be problems at both oxygen filter and oil filter so that they should be cleaned up. But I don't know how to do or even what exactly I have to do so(rather not to go to service center). I am in Finland and car center near my place always charge me amount of bills whenever I go there..!

The injection system warning lamp isn't related to the oil filter. It's telling you that somewhere in the system there is an intermittent problem - if you have the car plugged in to a diagnostic testing machine it should be able to tell you the nature of the fault.

My Marea one comes on every now and then, maybe once a month for half a minute or so then goes off. According to the manual, this isn't something to worry about. If it comes on frequently or stays lit for a length of time then it needs attention.