W218 optional ECU software updatr

[rtfm]

I believe that the ECU update in question may be the update that removes the 'defeat device' (aka 'cheat') from the ECU, i.e. the software bit that tells the car to be on its best behaviour emission-wise while being tested on a rolling-road....

There were some concerns that this ECU software update may adversely affect MPG though.

Having had the Euro 6 software update done on my GLC 220d some months ago, I can definitely say that it has had a detrimental effect on short and/or urban journeys. My guess is that my mpg is probably in excess of 10-15% worse off. Longer, out of town journeys seem to be unaffected or very little reduction in mpg.

The car has been driven mostly in comfort mode.

Please note that these observations have been made in mostly warm ambient temperatures of 20 C plus.