will lightweight wheels help?

[thebarber]

im not asking for the yaris, im asking for our 03 vibe gt (equipped with 2zzge and 6spd manual)

currently its winter so economy isnt great (about 9.5-10L/100km)

i picked up some oem toyota 17's last year (from canadian TRD edition matrix aka m-theory in the USA), but they weighed in at 47.5lbs for the rim/tire combo....i think the wheels themselves are about 22lbs

i drive mainly in the city taking my kids to/from school and running errands (as im a stay-at-home dad)

would switching to a lightweight wheel like the enkei rpf1 net me much, if any, increase in fuel economy? i realize the savings garnered by lightweight wheels will not pay of the light wheels....but what kind of increase can i expect? 5%? 1%?