I realize that I am replying to an old post, but what I have to say may be very relevant and helpful to many Nissan Maxima and other model owners. Some, will become rightly furious.
I had the same oil consumption problem with my 2003 Maxima. Each time I went to the dealer, they basically played dumb as to what could be causing the problem. There were no external signs - no leaking, no smoke, etc. When I asked if they had ever seen anything like it - there answer was no. When I asked what is the usual cause? Their response was that owners were not changing oil at required intervals.
The problem with excessive oil consumption that became noticeable at around 70,000 miles, eventually took my engine out. Luckily, I removed it from the Nissan dealership where it was towed and had it taken to a garage - owned by a Nissan trained mechanic - previously trained at that same dealership. He recognized the underlying cause.
The excessive oil consumption was caused by faulty catalytic converter design. As the catalytic converters aged, they produced a sand like substance that was being sucked back into the engine during the common negative cycle. This created a comet like substance that created excessive internal engine wear. As engine oil was drawn into areas it should not be and burned off, it further accelerated the catalytic breakdown process.
IMPORTANT: This was a known failure by the Nissan designed catalytic converters. The proof can be found in the Nissan Sentra Catalytic Converter Recall for 2003 - 2005. Refer to Nissan Service Bulletin Number NTB08-023 for model years 2003, 2004, 2005 and Service Bulletin Number 501 for model years 2003, 2004. (NHTSA # 10024146 and 10018243).
Each Nissan vehicle owner that was impacted by this would have had a difficult time seeing the forest for the trees. Each would have been looking for issues for their particular model. However, this issue covers wide spectrum of models. For example, the Maxima 6 cylinder engine can be in the Pathfinder, the Altima, the Infinity, etc. How many models use cats produced by the same manufacturer?
The shell game: Nissan and the dealerships have had great incentive to divert attention away from the real cause. Why? To avoid a wider recall than with just the existing Sentra one.
Do a Google search and you will find some amazing coincidences. When Nissan was forced to honor their warranty, engines AND catalytic converters were often replaced without an explanation. When owner solutions were provided by dealers, the engines were replaced, or rebuilt without dealing with the cats.
Here is a clincher: Also reported is that, even though the catalytic converters had failed, the check engine lights never came on. Many do not know that the internal diagnostic computer can be made to ignore any area. It would be easy to make this happen simply by a normal firmware update that could take place anytime it is hooked up to the dealership's diagnostic computer. My computer did not report anything wrong with my Maxima cats even though they were almost non-existent and had much of this dust. One cats material was a ball the size of a small fist - sometimes blocking the exit of the exhaust, causing a loss of power. Also, searching online, you will find reports of mechanics acknowledging that Nissan stopped the computer from reporting Cat errors.
In my opinion, there has been a wide ranging cover-up about the Nissan Cats. This is something that should have been an obvious concern of U.S. Government lawyers when the original Sentra recall happened. Problem catalytic converters are not just restricted to the Sentra.
Oh, yes. I replaced the engine with a 84k used one. And, it had the same problem as the previous one. 1 quart of oil per 650 miles.