Before I started to look for rims, I wanted to know how big of a difference the mpg would drop with 19"...

How much more do they weigh than the stock rims?

i noticed in the city it took upwards of 10% ... or about 1-1.2L/100km more. on the hwy it was more like 5% area. its slightly noticable but if you got the 2.5, its one of the leading fuel efficient cars in its class. its hardly worth worrying about. i was averaging 9-9.5L per 100km of mixed driving/short hwy.

btw, my nismo 19's with mounted falken 452's (245/40) weighed in at 49lb.