Hello waqas,
It sounds like you have a very heathy engine. Yes these engines, when new or kept healthy, used very little oil. Normally they would not use a quart of oil between 3,000 mile oil changes. Often times not any noticable oil usage at all. The high oil consumtion figure in the BBB is "allowable oil usage" and is confused with what is "normal oil usage when new".
I have serviced many of these cars since just off warranty new and know this to be a fact.
Everyone else should not panic, Mercedes knows time and miles takes a toll and has a fairly high allowable oil usage rate due to common wear.
If your engine is oil fouling spark plugs and bellowing clouds of oil smoke you may have to do repairs.
If your engine has less than 150,000 miles on it and has never had the head reconditioned, a valve job (head reconditioning) will solve oil consumption problems 90 % of the time ( a risk well worth taking when faced with the cost of a major rebuild). If you do have to do a total break down and rebbuild, do not scrimp on pistons and rings. Bore the block and install new pistons and rings.
Just replacing the piston rings in old worn engines will usually not solve the oil consumption problem.
Oil consumption figures inbetween no usage and high usage may be the result of normal wear, allowing some wear to remain in re-worked engines (valve guide clearences, cylinders etc, greater machining clearences than factory, or improper assembly (loose valve seals etc).
Pay attention to "rate of change". If something is going on you will see the consumption getting progressively worse!
Extended high rpm engine speeds increases oil temperature dratically. and a little more consumption is normal.
I used to run a Rallycar (with w113 engine) for long periods over 4,000 rpm and frequently up to redline. After a 800 mile event I would normally use about a pint of oil or less. Under normal running it would not use any noticable amount. This engine had 150,000 miles on it with only a recent head re-conditoning.
Joe Alexander
Blacklick, Ohio