Ok, then it's abnormal oil consumption.
- How old (mileage) is the engine ?
- What oil you put in there (viscosity) ?
- blue smoke @ exhaust ?
- no visible leak ?
- traces of oil on garage floor ?
There is (at least was) a consensus between mechanics that oil consumption of 1% vs fuel would be considered as the very maximum "normal" lost.
1 liter oil for 500km is way too high, unless your car guzzles 20l/100km...
Regards, Bernie