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I still disagree. . .
My dad drives the same car. He had 185 60x15s downgraded to 185 60x14s and up 2 mpg(he drives several hundred miles a week(100-120 miles per day)). I dropped from 225 40x18 to 185 60x14 and saw a jump of 10 mpg, no changes in driving route or any other vehicle aspect. Changing the tire width had an impact I agree but reducing the tire diameter meant I needed less fuel to reach an rpm because the wheel was smaller and because it is much easier to rotate a smaller lighter tire than a larger heavier one. Also the larger the rim the heavier it is going to be. dropping fro 215 to 180 you will see gains but you also see gains from 18-smaller. Another important factor is 14 inch tires are dirt cheap. I got a set of four pirelli snow tires(new) for 100 bucks, and 4 of P4 all weathers(new) for 112. After checking a couple of sites, the cheapest 18 inch tire is 90 bucks. cheapest 14 is 35.
Price gap is 55 bucks per tire. . .
you have to get more than 4 mpg gain having the 18 inch tire before you save any money. it costs 240( i assumed 2 years for tires and 15,000 miles a year and gas averaging 4 a gallon) to replace those 4 tires.
You save 55 bucks a tire, and gain the 185 width without stretching your tires, while also gaining more mpg(you end up driving slower than you think, and MUCH less rotational mass)
I save lots of gas and lots on tires.
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