I don't disagree with you Dean on the spares issue etc., but as I see
it is you add up the cost of the engine and spares and then the fuel
used over 40K hours or so and see where the real $ are.

I also don't disagree about two different vintage engines; newer are
more efficient, but look at the SFC on a CF6 of about 40K thrust and a
CF34 of 9K thrust (same vintage) and I bet the larger engine has the
upper hand; maybe not.

Good discussion subject and it would be interesting to hear from
others who know what they are talking about. Obviously anything I say
comes from being around these things, not because I profess to be any
kind of authority. Any aircraft turbine engineers out there? Neat
thing about aviation is there is always something to be learned.