Pet hair is an interesting counterexample to the usual rule of less (water) is more (efficient).
Seems to me the best way to get rid of pet hair is to remove it with air rather than with water, since when wet it tends to stick to everything. So how'bout this: Before washing, run for five minutes in the tumble dryer on "air fluff" mode (no heat) just to loosen and remove the pet hair. Then into the washer and see if there's any more pet hair left to come out (e.g. a GE Filter Flo or equivalent, with the lint-catcher on the agitator post, so you can examine the fluff balls for pet hair).
Re. vehicles: Dodge Caravan minivan, which I need in order to haul equipment & coworkers around, but is more efficient than a regular-size van. 25 to 27 mpg highway depending on speed, as of last time I checked (a couple months ago).