I suggest you take a look at a few things. Air filter ,fuel filter ,spark plugs and fuel quality your usng. I would leave the fuel filter for last as that is probably in the fuel tank along with the fuel pump.
I have started to use 91 octane because of this very same issue.Does anybody make a habit of using only premium during summer months? Any associated issues?
I tried 89 (instead of 87) here in KY for one tank, lost about 7mpg. Although im not convinced the dealer didnt do something during my last oil change. I was getting it done at the closer Chrysler dealership but needed some warranty work so i went to the Mazda dealer. Within 1000 miles the oil smelled like gas very strongly and the MPG has sucked ass ever since. Im about to change it early and see if maybe somehow they used the wrong oil. I dont remember anything like this happening last summer even running the A/C all the time.I am talking about 91 octane in North Anerica.
Europe has a different number system for anti knock ratings.