Consumers though shouldn't be in that position, not in this way at least. The way it is supposed to work is you choose from a variety of approved, legally-sanctioned alternatives. You want a gas-guzzling, smog-spewing (comparatively) vehicle? No problem; pay the gas guzzler tax and have at it, because even this arguably "poor" choice is within the legal limits. The laws are intended really to constrain the parameters of acceptable decisions. You can encourage people to drive economical, clean cars, but you won't convince everyone, often for fairly valid reasons. So you set limits that minimize damage while maximizing choice and market freedom. So the ethics of the decision is much more a gray zone--if the car really was that bad, it couldn't be sold, so you're off the hook.
Here, it was flat-out lying. People thought they were making a good ethical choice and getting a good benefit (performance and economy) in the bargain. Even if they were not at all concerned about the environment, they did nothing ethically wrong--and I'm not convinced that in all cases it's more ethical to ditch performance in favor of better emissions; it depends a lot on the actual numbers, among other things. VW, on the other hand, did indeed do Bad Things, ethically and legally. They not only violated specific regulations and laws, they violated the unspoken compact of the marketplace by subverting the process by which people come to terms with complex issues like balancing different attributes (performanc, economy, emissions, costs) in a market system.