Problem with the fleet approach - at least here in Ontario - is the cost of insurance.
The bare minimum, least expensive insurance costs me ~600/yr to add another vehicle (liability only - no protection of the vehicle itself). Hard to save money in that situation (if that's your goal), unless you're driving a LOT, or driving a serious gas hog, or both.
EDIT: while on the topic, can I gloat please, please, please?? I put $92 worth of fuel in the Firefly last year. (2 full fill-ups, plus a splash.)
And a bunch of electrons in the EV. I really don't pay attention to gas prices.