imagine your tyre grip to tar surface or use your hand to experience it.
Try to use one finger to paste on your house cement and rub hardly on it. You will feel like nothing except your finger is dirty. Ok now, what about 2 fingers? Is it become harder? what about 3 fingers? harder than 2 fingers?
If answers for above are yes, then now back to your tyre. Let say 1 fingers wide is 175, same as your original tyre wide. 2 fingers are 185, bigger than your original tyre wide by 10mm. 3 fingers are 195, bigger 20mm. When the tyre wide become more and more wider, your car will need more power to move. Then come to a concept,
more power = more fuel
Come to a conclusion, bigger rim will affect more fuel consumption. But one benefit you gains from bigger rim, your car will be more stable while doing sharp turn.
Happy modding!
Above comment(s) or suggestion(s) are only my opinion.