Ive been following the oil life monitor on our 07 Impala and my 03 Trailblazer with the 4.2 inline 6. This engine takes 7 quarts with filter change.
Ive always used my OLM. I dont have the DIC-- so my light comes on... It does not display a % oil life left...so I change when the light comes on.
BUT... I do trust this system. As long as you use oil that meets the GM Specs- and use a quality filter- the oil will degrade in a known fashion that the OLM can accurately predict.
My 03 Trailblazer just turned 138,130 miles today. over a 2 week period Dec15 to Jan 2 (4 days of driving) I racked up 3200 miles of pretty much non stop driving. I was loaded up-- enough to drop my rear end 4 inches... thats alot of weight... I drove thru the cold sonoran desert and up and down some hot humid mountains thru the Mazatlan area- and finally into Guadalajara... I came back to Los angeles with 3200 miles on the oil--- and will leave it in there for another 5 months at least... I know the OLM will come on when I have somewhere near 11,500 miles (from my past 3 trips to the same location).
I use nothing but regular DINO oil 5w30 Valvoline.....
When my engine passed the 100K mark I wondered.... so about 25 miles shy of hitting 104,000 miles--- I drained oil and took a sample. (OLM had not come on)... I had the oil analyzed... I also did not reset the OLM...
as you can see from the results below- the analysis said I could go a little further with the oil.... and sure enough.. my OLM came on about 300 miles later...
this would indicate that the GM OLM was right on with the in lab oil analysis results..... pretty impressive I think....
I have continued to do these long 10-11,500 mile oil changes....
This is a pic of how heavily loaded I was this past december on my trip to Mexico... I think 4 inch drop is significant on an SUV- hard to see the rear wheel well--- but when unloaded-- its sits much higher....
I plan on replacing the TB with the Traverse... but my TB is still performing great.... By the way... the trip was MOSTly highway... and non stop... I was able to see 21 MPG at 70-75 MPH and with all this weight. (since it was all highway with cruise set). At home I see 18MPG with combined highway/street.
When I get the Traverse.. I plan on doing oil changes based on the OLM.