That depends really on how fast the car was going. To do deadly damage to something considered hardened you'd have to be going really fast. Even disrupting them physically wouldn't stop the summoner from recalling them.
Imagine rolling Conjuring 6 against a target number of 1. You'd smoke the drain 1L easily, you'd only spend 6,000 nuyen on materials (less if you made them yourself) You'd only spend 1 hour drawing the ritual circle, and 1 hour on each elemental to summon, and you'd end up with at least 4-5 favors for each elemental. Significantly more "bang for your buck" considering only rolling 1 or 2 successes on a significantly more powerful force 6 elemental.
The target numbers stay the same if you go for force 2 elementals, twice the time and cost involved but with more potent spirits. So perhaps the best type of "horde spirit" is force 2. They get 4 points of armor against normal weapons, a combat pool of 4, and a natural attack roll of 2. They're generally faster than most unaugmented people with a base initiative of 12.
Remember also, that not only are lower force spirits easier to summon, but they are also less detectable and blend in with their summoner's aura better. I knew a street-mage who always loaded up on high-power spirits, fetishes, foci, the works. But he never realized that packing all that mojo makes you light up like a Christmas tree on the astral. I'd rather have my 3 points of automatic spirit/focus Masking give me 3 force 1 distractions with 6 favors each, than a half-concealed rating 6 monster. Discretion is always a necessity in this game.
