Not so much these days - Autos generally today have more forward gears than manuals so they can provide that power to the car at lower engine speeds. The AM6 is a six speed Auto box. The current manual boxes fitted to a lot of PSA cars are 6 speed (depending on engine type and size). But some of the new generation of PSA Automatic boxes are 8 speed, so will be more economical.
Having said all that, when comparing the 2.0 HDi 138 engines below, one with Manual 6 speed and the other an Auto 6 speed, you can see the Auto fares poorer both in consumption and emissions: These are the official PSA figures for the C5 X7 2008 on for the engines specified.
|-||Marketed versions||2.0 HDi 138 hp BVM|
(Manual 6 Speed)
|2.0 HDi 138 hp BVA|
(6 Speed Automatic)
|-||Engines: - gearbox||DW10BTED4 - ML6C||DW10BTED4 - AM6|
|Urban (EEC)||Consumption (L/100km)||7,9||9,9|
|CO2 emissions (in g/100 km)||209||262|
|Extra urban (EEC)||Consumption (L/100km)||4,9||5,5|
|CO2 emissions (in g/100 km)||129||146|
|Combined (EEC)||Consumption (L/100km)||6,0||7,1|
|CO2 emissions (in g/100 km)||157||189|