Let's see... I live in a rural area and have 3 kids (with a 4th on the way). My mini-van gets 20ish miles to the gallon and my job is 12 miles each way from home. Add in baseball practice & games for the 3 boys 4 nights/week, dropping my step son off at his birth mother's every Saturday, going to the grocery store, pharmacy, etc. and I'm filling up once a week for about $60.
What vehicle do you recommend that is smaller but would still hold my husband and four children in addition to getting me to/from work every day? My husband already drives an 1988 Ford Escort because his job (like so many other people in our area who must commute out of the county for work) is 30 miles each way - but his vehicle will only hold 4 people total - not exactly a "family" car.
We all have different needs based on our lifestyle and family size. Frankly, I'd think gasoline isn't the biggest expense once you've decided to have four kids! :)