If your only consern will be fuel economy then I would say no way on the points euromodder pointed out. You will spend money on more expensive rims and wheels and get worse mileage.
I would buy either that 185/65R15 or even more popular 195/65R15. If you want to even maximize your bang vs buck buy them used. Used tires roll better than new ones...
If you want new looks to your rims go with lighter 15" ones on the market, cant go wrong there. After that you attach some cool clear pizza pans to them and you got the winning setup in any conditions
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