However, some points about your reply.
I was not saying that ‘poorer power equates to more economy’ per say… I am sure the Guru’s at Mercedes and Renault are fully aware of what you say… and evidently Renault got the maximum power they could from their fuel engine combination whilst maitaining their reliabilty…. but if that is the case, the simple laws of physics state power in is equal power output plus losses. Thus given similar losses and maximum efficiency from the engine (as tuned by the engine Guru) then less power equals less fuel. Now given that running an engine leaner will lead to greater heat generation ans thus problems with reliability, Renault ended up less power…

Going back to my statement earlier, if the Mercedes is a better package ( due in general to less losses be in whatever form they take) then They have the ability to detune (control power output) and maximise fuel economy or instead re-optimmise for power even during a race, lap, or corner and go back to the gain over Renault they had.

Thus Merecedes is still sitting pretty. Ferrai are of course in the worst position as although they can achieve similar BHP to Mercedes they do this at a fuel cost relating to the inefficiencies whithin their engine.

however, up until this point, engine manufacturers have been working with their fuel partners to extract every last bit of power from their engines, and fuel consumption has been a very distant concern. now that’s changing and it’s not beyond the capability of any manufacturer or their fuel partner to develop something that concentrates more on ‘economy’ (and also increasing fuel density, in order to reduce the volume of the fuel tank), especially with the relaxing of the fuel regulations for this year.

as for mixture strength, engines will be run on the dyno’s with full lambda control and this will feed the ECU so they have all the data they need in advance about the fuelling required to hit their targets. they normally also run full lambda sensors (i.e. one per cylinder) in free practise to double check the numbers, but then take them off for qually and the race to save weight.

Great stuff guys!