VW did something in the US that's explicitly illegal under US federal law (employ a "defeat device" to disable emissions equipment outside of testing). For the

VW did something in the US that's explicitly illegal under US federal law (employ a "defeat device" to disable emissions equipment outside of testing). For the most part the other auto manufacturers seem to be tuning/optimizing their emissions equipment specifically to pass the test cycles but are not going so far as to outright disable it outside of them like VW did.