I am in a similar situation. My two vehicles are a Heavy Duty 6 liter longbed that sucks down 39 gallons with each pull at the pump, and a 750cc motorpony that gives me 50mpg in a head wind. I only drive the truck when I need to and have given some serious thought into trading it out but it never fails that something comes up that could not have been resolved easily without having that fecking truck. Most recent was the wifes car. Timing belt adjuster tanked. Found a guy out of town that replaced it for pennies (comparitavely) but had to tow the car 40 miles. Would have still been cheaper to hire a tow truck to haul it rather than going to a local shop but having that truck saved a ton by just renting a trailer.
Monies I dumped into performance mods on the bike.
Fingers crossed the mpg hasn't taken a dump.