Yeah this is my story too. I rarely drive my car during the week but it carries me to the mountains for the weekends. I do ride a moto a couple days a week but it barely uses any gas.Been commuting on the bike then burning through a tank getting out on the weekends. Could be worse.
I'm lucky that my ride too work is mostly downhill (no sweat), and that I have an office where I can stash clothes. Between my bike, moto, and public transit, I almost never drive my car to work.