I also fly the smash 8.
To answer original post - Fuel saving on the ground, at current time, only Dash 8-300s are allowed to single engine taxi. However, due to a lot of new upgrades, some new CAs would like to keep the engine running till he or she get used to "taxiing" the plane.
On the flip side, Dash 8-100 are not allowed to single engine taxi yet. The main reason - nose wheel. According to what I have heard, nose wheel strut are not strong enough. Jace, you can ask your CA in regarding with that. I believe you and I going to see single engine taxi fleet wise soon enough.
Enroute phase, for 100, it burns about 600 lbs per side. However, I do not fly 300 enough to tell how much Jet A it burns.
I hope this answer your question.