[quote="marlin758"]
Just a possibility that if the engine was rebuilt and the oil filled to the top mark on the dipstick then when the engine was started a lot of oil is needed to fill the oil filter etc.
If the oil level wasn't checked again after the engine had been run then that's where your oil has gone
[/quote]
A very good point!

I also done a bit of googling last night and it seems a lot of people seem to us a quart of oil every 2k miles.
These posts of "quart" oil im guessing is Americans! I'm not actually sure how much a quart is

)