[mft_]

Totally different, isn't it?

Presumably the Vauxhall mentioned would provide exactly the measured MPG when driven at the correct speed by any owner in the real world - hence the 'flat spot' noticed.

The defeat concept you're referring to (presumably VW's) was set to only function during a test, and not in the real world (AIUI).

[londons_explore]

VW's defeat concept was set to function only at the exact RPM's used during the test. If a real-world customer were to use those RPM's and conditions, it would activate too. In fact a CCC talk showed that 5% of regular driving activated it.

Perhaps about 5% of regular vauxhall driving was in those flat spots...

Seems the same to me.