190 E oil cunsumption

Hi,

My girlfriend has an 88 190 E 2.3 , over 100K miles, and it is going through a quart of oil almost every 2 - 2.5 weeks! There aren't any obvious oil leaks; no spots on the garage floor etc. Its also not smoking noticeably either. Any thoughts? I'm afraid that an internal engine job would cost more than the car is worth, although I really don't know what costs would be like. Any input would be appreciated!

Thanks in advance,

Tom