2012 Mazda 3 SkyActive POOR GAS MILEAGE
I have a 2012 Mazda 3, SkyActive 2.0. I presently have 64,000 miles on it. About six thousand miles back, and about 7 months ago I noticed my gas mileage falling. With a 17 mile one-way drive to work, half freeway, and half side streets I would average 34 MPG. Now, I am averaging about 30.3 MPG. I replaced the spark plugs with iridium plugs - and I did not gape them, because I read that iridiums don't need to be gaped. These new plugs did nothing for the mileage. One symptom is that it is not shifting properly in automatic mode. At first I could feel it, then I would go to manual and find it was in 5th gear going down a sloped road. The idle levels out to 800 RPM when started cold.
Another symptom I noticed, and found in the Mazda 3 forums... My headlights will intermittently flicker when applying the brakes. I saw the forum thread on this issue and saw that it was a software update. Could the poor mileage be a similar software fix? I really do not trust the dealerships to get an honest answer. I live in Southern California, where top dollar service charges are always standard.
I would appreciate any/all input on this issue.