In addition to a bad PCV valve or external oil leaks, there are two other factors that lead to increased oil consumption; which on a 9 year old, 85,000 mile engine, are much more common than engine wear. One is the valve stem oil seals losing their elasticity. Replacing the valve stem oil seals will often make a significant improvement in the rate of oil consumption. By using specialized equipment; this repair can often be done without removing the cylinder head.
The other factor is often not considered by mechanics or owners. It comes from piston rings and valve stems sticking from carbon and sludge deposits. The additives used in modern gasoline for emission reduction have a downside of leaving heavy carbon deposits in combustion chambers and on valve stems. These deposits can actually build up to the point where they increase the cylinder compression ratio to the extent that the motor starts to knock on the recommended fuel grade. I once encountered a three month old Toyota Celica that developed a heavy metallic knock which was so loud that I advised the owner to not drive the car any further; and to have it towed to the dealership for warranty repair. When I saw the owner a few weeks later; I asked her what the problem turned out to be. She replied that the dealership ran some carbon solvent through the injectors, and it totally eliminated the knock. The mechanics warned her to stop using the off brand fuel she had been using; and only use Chevron gas from then on.
There are two products which are available today that I have found to be particularly effective in freeing up sticking piston rings and carboned valve stems. They each work in different ways. Chevron makes a fuel additive called Techron, which is designed to be added to the fuel tank just before filling it up. During the next 50-75 miles of driving; this unique product will clean the valve stems of deposits so well that it often makes the car run better than it has run in years. Only afrer experiencing the effects of this amazing product; can it be realized how big a difference these carbon deposits make on the way the motor runs. Techron can be bought at Chevron gas stations, Wal Mart, Auto Zone, and Checker, Shucks, Kragen, Murray, and O"Reilly Parts stores.
The other product is a unique internal engine cleaner and lubricating formula made by a company that mainly supplies major industrial companies. The product is called Kreen; it is designed for one pint to be added to the gas tank, and one pint to be added to engine oil; preferably at each oil change. This non toxic product has gained a wide following of enthusastic users. I have used it with consistent success for many years, and have seen it dramatically reduce oil consumption in older engines. It is manufactured by Kano Labs, in Nashville, Tennessee. THey have a special offer on their website: (www.kanolabs.com)