Math on having a second vehicle

I had 2 or 3 vehicles most of my life til 03 and then I got down to just my truck. My truck was my one and only vehicle for over 9 years. I'm on a van pool to work now but I used to put on 12k miles/yr, commuting. My 03 CTD was getting exactly 21.0 mpg in those days of fuel w/sulfur. I did calc's on just the fuel savings, if I had a 28mpg car and the fuel savings (I think it was ~$90/month) would have only covered the insurance on a second car. A year ago, we decided we wanted a 4wd SUV, or something, to go into the desert and mtn trails so I found a nice 99 Jeep GC for $4200 and we're loving it. It all depends on what you want/need. I will probably go back to one vehicle, some day, when we get tired of this exploring business. Convenience is another factor. I'd much rather run my errands in the city with a smaller vehicle than a LB 4 door truck. Craig