Not sure about the rolling resistance of aftermarket tires but I noticed since they are a bigger tire and they are all heavier. This would affect mileage a bit plus acceleration. Not by much obviously but I'm thinking I will stick with the stock toyo tires when I need replacements. Decent all around tire. Ride, handling, all weather. Plus light weight. Mazda skyactive cars are all about getting the weight out, getting the heat out, and Jinba Ittai. Low weight = more efficient, better handling. Low heat = higher compression and better efficiency. Jinba Ittai = Driver and car as one - responsive, tactile feel.
I have 195/50/16 Dunlop Dirizza's and it has affected mileage and speedo by about 3. I am enjoying the sporty handling an the lower gear ratio of the smaller diameter tire. really handles dry corners well now, but there is a trade off. I have no rubbing or clearance issues what so ever. Lowers car about 10 centimeters and looks nice. Wheel gap is not noticeable but lower ride hight makes the car ride firm and sporty. I am on OEM rims and suspension and ride is firmer- sportier.
Hey you might want to watch this video on scrub radius before you change tires. I went with 50 series on stock rims and it may be a bad idea. you might want to keep the overall diameter equal with stock. I have noticed great handling but a little squirm with 50 series on stock rims when breaking hard. if you go to low profile you might want to go to 17 inch rims to keep scrub radius as close to stock as possible. I am enjoying the great cornering but I think I will go with a 55 series on my next tires unless I get plus one rims (17).