We just bought our 2021
We just bought our 2021 Ascent this winter. We had awful mileage (AVG of about 18mpg or less) to start with. We had all the fluids changed (oil, CVT, both diffs) which helped a little. Especially the rear diff pouring out black material. When our dealer did that they noted an exhaust manifold gasket leak they said was VERY common. When that was replaced I've noticed MPG climbing towards 22mpg.
I also noticed the oil temperature would finally start to climb towards its usual 190 degrees faster than usual. It used to never top 170 even going 75 on the interstate. Seems to me it was running rich. We also did some deep snow driving (deeper than the intercooler), don't do what we did, that got the temps up over 210 and it has ran nice since then lol