So you're saying you have a Grand Cherokee now and thinking about getting a second vehicle that gets better milage? if so, don't forget to add additional taxes, insurance , maintenance etc into your calculations. That $1000 a year "savings" gets eaten up pretty quick.
Since I started my first big boy full time job in 2007, my wife and I had always had 4 vehicles (at least). I had a DD car, she had a DD suv/crossover, we had a diesel 3/4 ton truck, and a rotation of various offroad vehicles. last year I got rid of my DD and the diesel for a 1/2 ton truck and haven't regretted it a bit. takes a lot of gas savings to make up for the ownership expenses.
From 2007-2013 I drove 100 miles per day. 2013 - current 70 miles per day.