City milage depends greatly on how much time is spent idling at stoplights, and similar.
I've logged trips back from a garage I rent a couple miles away and frequently more time is spent at a standstill than moving.
Even when in good tune and stock set up, the larger engine will drink more fuel when idling.
Add to that many of the v-8s are hot rodded and have by nature poorer idle efficiencies, fuel consumption per minute of idling gets even worse.
