because its a car with an engine, like all cars it needs oil to run.
^ This guy perhaps didn't understand your question, or was being rude. The correct answer, if your car is Burning oil, (Have to add oil between oil changes) your car either has worn valve seals, allowing small amounts of oil into the combustion chambers, or badly worn piston rings, allowing the same, Or a combination of both, It is likely bad valve seals though, unless you drive your car very hard, Or have a lot of miles (Over 150k) Any reputable mechanic could change the valve seals in a day.
According to the 2002 Ford Focus Owner Guide : ( 5W-20 ) engine oil is recommended
Motorcraft oil 5w20
5w/30
no
5w-20
We use Pennzoil 10W30
yes use Mobil1
Use a good synthetic oil, available at Wal*Mart or Auto Zone.
I use 10W-30 Pennzoil. Use 5W in the Winter.
PAG 46
i have read on forums that you can it doesn't hurt.
We use Pennzoil 10W-30