No engine modifications, mixture of freeway and country roads. The car has an service indicator for oil changes, and it's been calling for roughly 20,000 mile intervals for me. I've been changing the oil once between its recommendations, and I think I'll continue that regimen. I changed the oil when this sample was taken, and used Mobil 1 0W-40 again.
Note that the 0W-40 stayed in grade over a long interval, even with the addition of 0.5 quarts of 5W-30 as make-up oil. (If it had sheared out of grade, I wouldn't have cared too much, because xW-30 is an acceptable grade for the engine.)