Do wider tires hurt gas milage?
Not sure but thought I would share my experience.
I have read other posts about wider tires hurting mpg and I do agree the added contact patch and drag should hurt mpg.
Just an update so you do not have to go back and look, but over a month ago I purchased new wheels and summer tires. I will keep my OE Austins for winter.
My new wheels are OZ Leggera HLT 18x8.
Tires are Bridgestone RE-11, 235/40R18.
From OE wheel width is up .5" and tire width is up 10mm.
The tire weight is plus 2 pounds from OE tires.
However the wider OZ wheel is much lighter, enough so that the new
Wheel/tire set up is 5lbs lighter at each corner.
So, today I made my first long run. Two hundred miles on a mix of 50 miles highway and the rest interstate. The highway part has many hills as you drive up and over the Cumberland plateau. The interstate part was at 75mph.
On this run in the past I have averaged around 31.5mpg.
This trip I averaged 30mpg.
Only one data point but it was a slight drop.
I can live with it as the summer tires give such a solid grip in high speed interstate turns. Wife felt I was taking turns too fast but there is no reason to lift as the car is not even phased by turns now.
Try some summer tires if you can and lighter wheels, as they help the feel and handling of the car.