BLACK oil in 3.6 direct injection engine
 

I have an 08 CTS with the direct injection engine, purchased in May 08, has 4,000 miles on it.

Dash indicator shows 69 percent oil life remaining. Uses no oil. Oil pressure normal. Runs great. No unhappy engine noises. My first time using Mobil 1.

I changed the oil and filter at 3,000 miles then 76 percent oil life remaining because the oil on the dipstick looked so black, and, indeed, was extremely black in the oil drain pan. Not just black. But BLACK BLACK!!! I didn't reset the "oil life remaining" indicator, but kept track of it on my own oil change record.

Put new Mobil 1 back in, used a Cadillac parts counter filter element, and now with 1,000 miles on the oil change, the oil on the dipstick shows that it is again very black.

Question: Is it normal for Mobil 1 to turn that black, that fast in other (direct or non-direct injection) engines?? Why is it turning black in this worrisome manner? Is it retaining its lubricity?? Is it okay to continue to run it? It couldn't get any blacker.

Seems to me that it must be some combination of acid and blowby that is causing the blackness, but as I mention above, the engine performance is fine.

I am well aware of GM's crankshaft revolution counting, oil acid/crapola dilution testing algorithms that are reflected in the "oil life remaining" readout. That aside, why is my oil turning so BLACK BLACK so QUICK QUICK???

???????