This is the pre-Ecotech engine, the 2.3 litre cast iron block engine manufactured in Saab's now closed engine manufacturing facility which was shared with Scania.
Fuel mileage has dropped - I think - it is hard to tell with seasonal fuel blends, elimination of MBTE, more use of Ethanol as the oxidizer additive, outdoor temperature fluctuations during winter, etc. I tend to get 27MPG on my daily commute, mostly expressway driving at 75MPH or more.
The current O2 sensors were installed 50,000 miles ago. The MAF sensor is still factory original.
After doing a little more reading it appears my only "problem" is too much fuel in the oil. Maybe the engine is running slightly rich.