I changed to mobile 1 for the first time at my last oil change and notice no increase in oil use (0.5 qt per 3k).
If you are still under warranty (if you are the first owner) you can have isuzu conduct an oil useage test and see if they will install a new engine.
Be happy you know it burns oil and now watch it.
Once a week top it off.
adding one qt of oil is a small cost to pay (but you are correct, it really shouldn't be doing this).