I'm not sure where to start on this episode. Not bottom of the barrel, but not outstanding either. It kind of strikes me as "what topic can we put a spin on next?", and the result is not all that focused.
Global-friendly cars are probably a good target, but it's like they weren't on the pulse quite as much as some of their other satirical takes. Very "okay, we've got the topic... now what to do with it?". "People who drive Hybrids are smug. Let's make a cloud of smugness; oh, and have them smell their own farts", O...kay.
Suddenly, in the latter stages of the episode, it abruptly becomes a Cartman episode, where, with Butter's help, he makes his way into the depths of San Francisco to bring out Kyle and his family, who he misses now that he has no-one to pick on. I think I would have liked this episode better if this theme had been introduced earlier, but as it is, it feels like an abrupt shift.
After the horrible start to the season ('The Return of Chef'), this is just a slightly uneven and very average episode. The season still needs something to really kick it into life at this stage.