Almost 3 quarts of dyno oil used in 5k miles - 2006 M45

[tytamto]

I have searched and read all the posts on here regarding oil consumption, and what is considered normal and abnormal. Seems that 1 qt per 3000 miles is rather common and considered OK. But almost 3 qt in 5000 miles?

In my 2006 M45 (37k miles now) I am using Castrol GTX 5W30, and do mainly long distance highway driving - typically on cruise around 75-80mph. It took me almost two month to cover 5k miles. On this oil change, I have redlined the car maybe 5 times - and my mileage record agrees - I average about 21 mpg. I hardly ever varies from 18-22mpg per tank.

I had a 30k mile service done a few month ago, actually did most of it myself. I have also sent my previous oil sample to Blackstone Labs and got very good results. Here is what they said (I will not post numbers in the interest of space - but all apart from Iron were within reported averages for the motor).

"On the whole, wear looks pretty good in the first sample from your Infiniti. Iron comes from steel parts, such as the cylinders. As all other wear read normally, we aren't too concerned about it but we certainly hope it reads lower next time. Universal averages are based on an oil run of ~3,500 miles for the 4.5L. If you're okay with wear at this level, you could push up to 5,000 miles next time. No harmful contaminants were found and your air and oil filters (silicon and insolubles) are working well, too. Check back at your next oil change for another look at wear."

Oil properties were within spec after 3500 miles on that sample.

And I decided to see how the car does with a 5000 mile interval. And since I drive mainly highway, the oil gets to temp every time, and therefore should last longer. I have a new sample that I will send next week. This time I used Shell Formula 5w30.

So to my main question... should I get the consumption tested at the dealer? I can stop by there on Monday, with my fresh oil and filter and start the process. Are there any key phrases I should use? I am hoping that if the car does burn through so much oil, they will provide me with a new motor.

Thoughts?