Car: Jag XF 3.0
Join Date: 10th April 2006
Thanked 2,774 Times in 824 Posts
An engine that uses more oil is most likely losing the oil via the oil control ring.
This is most likely because the running in process was not done as well as it could have been.
If the car loses oil because the ring/bore interface is not as good as it should be, then the chances are that the pressure ring(s) are also not working as well as they could be and the cylinder pressures will be down (resulting in lost power/efficiency).
The cars most prone to oil and power loss are the ones that were run in too gently (glazed bores), but you can get the same symptoms from other abuse, such as thrashing when cold, or using cheap oil (or not changing the oil).
But - it's quite possible to lose oil in other ways, and it's possible that your oil rings are not working as well as the other rings. Possible, but not that likely.