MK2 Golf 1.8 Engine

Hi

 had a question

A mate of mine has a 1.8 MK2 golf automatic which seems to be burning oil
There is no oil leak however every 4 weeks or so he has to top it up with a liter or so with oil

Just wanted to find out what could be the possible causes  and fixes without opening up the engine if so..

Thanks

No easy fix if its got no leak .. just keep topping it up or spend £££ .. possibly, Rings,cylinder wear, valve stem oil seals ,   . How many miles has it covered

Its done about 60k or so... not too many...