My Mk4 fiesta 1.4 zetec se engine is using about a half a ltr of oil a month (about 700miles).

It's not leaking out of the engine as the underneath is oil free and no drips on the drive where it's parked up. It's not throwing any smoke out of the exhaust when driving, so im not sure where it's all going !

Does anybody know what could be wrong ? i would imagine it will be serious.