Lambda 1 means the 'ideal' stoichiometric air/fuel ratio (AFR) of 14.7:1 (i.e. off boost constant throttle cruising = 'decent' lol mpg).

Richer mixtures are represented less than 1 (e.g. lambda 0.83); and leaner, greater than 1 (e.g. lambda 1.25).

 

In MOST conditions, 70 mph on the motorway will be at 14.7 to 1 AFR as controlled by the lambda sensor in closed loop.

Incidentally, taking swept volume into account, fuel consumption will be affected by the increase from 2.0 to 2.1 in the order of 1.75 mpg (average) on light cruise.

 

EU should revise their 75 recommendation down to 70

 

OMG - it's a good job then that I took my 2.1 out (sadly to replace it with a 2.35 ).

Fuel consumption generally shocking in all Subarus, but who cares? It's not a car I bought for its fuel frugality.

Re the drive, there is more torque than might be expected with a 100cc increase in capacity, due to the longer rod stroker nature.

I did a 2.1 when my 2.0 died, otherwise I wouldn't have bothered.