I need some advice from the community. 2014 Cruze Eco 6M/T. Bought new and babied to 92k. The whole reason we bought this vehicle is for the gas mileage. I hypermiled with it and routinely got high 40's and even low 50's MPG averaged for the first few years of ownership. No problem. We were happy. Then things changed. The last maybe 1.5 years and 20k the mileage has dropped like a rock. I am talking an average of 36mpg indicated, ~34 calculated. That is still hypermiling, with 90% highway driving, cruise locked in at 65. Driving conditions are mostly identical. Tires overinflated. Synthetic oil and trans fluid. Techron every oil change. Premium fuel only since the beginning. New air filter. No check engine lights. No obvious issues. I thought maybe it was the PCV issue, and found that the orange valve was gone. Intake manifold replaced...no change in mileage. In the past year I have done the ignition coil, plugs, intake manifold, and battery terminal.
It is really frustrating because we bought this car new to keep it for at least 10 years and 200k+ but with such a gas mileage drop we are struggling to justify it. I don't really want to bring it to the dealer and pay just to have them tell me "no problem found".
Is it worth doing a MAF cleaning? Any other things to check out?
Thanks in advance!