The oil is probably going out the exhaust pipe. You didn't mention how many miles are on the car, but it's normal for an engine to burn a bit of oil. In newer cars, oil consumption would be low enough that it wouldn't use up a full quart (liter) between oil changes, but as the engine gets more wear, it will burn more oil. 1 liter between oil changes is NOT a big deal. Just check your oil levels a bit more frequently and top off as necessary.
If it starts using a liter in 1000 miles or less, THEN it's time to get the engine checked out by a competent mechanic.
My guess is that you have a bad head gasket and that your oil is leaking out somewhere. It's probably disappearing between a combination or your exhaust/tailpipe, dripping down your engine block, and mixing with your radiator fluid in you radiator. Blown head gaskets mean bad news and no cheap fix. Have you ever noticed any oil/fluid puddles under where the vehicle had been setting? Or have you ever looked into your radiator and notice that there were some blackish swirls mixed in with the neon green radiator fluid? If you have, you have a bad head gasket.
if it's not leaving a puddle on the ground, it's not leaking, It has to be burning it. With catalytic converter's & various emission control's you have to be burning it & you just can't smell it.
The oil is definitely leaking somewhere. The question is where? And how difficult/expensive will it be to fix?
It's an 06' Lexus IS250. I put oil in it and then one two months later before the 5,000 miles are up I have to add more oil. Where is this oil going?
