Ok Cosmo, we are starting to make some headway into the 'misunderstanding ' that you pointed out. I agree that there is a level of misunderstanding on this topic but am not convinced that it lies with me.
Every decision I make in the cockpit is a conscious, considered decision, based on the facts at hand... Not an automated decision based on old wife's tales or "that I always do/need so".
You are quick to point out that adding an extra margin is a wives tale but it's genesis may lie in truth. Your conscious, considered decisions, based on facts at hand will be drawing on your knowledge base and the learnings you have made over the years in order to make the decision. It is neccassary to have self confidence in that knowledge base, but also to be prepared to re-jig it if it is found wanting so that your decision making skills evolve as you go. I want to question that knowledge base without it seeming like a personal attack .With that said, I am more than prepared to eat humble pie and rethink my alt selection if you can direct me to where I have misunderstood. Your last shot at directing me there fell short. I'll show you where so that there is no confusion.
Service ceiling is determined at the speed for minimum drag = minimum thrust required. Minimum thrust required = Max Range Cruise. MRC in the FMC is ECON cost index 0 (no wind)
Only two of those three assertions are correct.
The speed for minimum drag does not equal the speed for minimum thrust required in a swept wing Boeing, and, Minimum Thrust Required does not equal Max Range Cruise in a swept wing Boeing. I agree that nil wind CI zero equals MRC.
So shall we sort out those basics before we move on to determining why you and Latetonite seem to be on the fringe of what B737ng pilots think is an acceptable way to operate the aircraft?
I'm glad you mentioned min drag actually because that speed is probably the only relevant speed to you when you are operating at Max altitude, that and Vmo of course. I have one question for you, in your flight the other day when you said
Coincidentally I had exactly this scenario last night, so I can back up with some numbers too. Cruising at 360 top of clouds with continuous light turbulence (what other usually report as moderate, for some reason). Max 381 with a 9 knots margin between low and high speed buffet (240 to 249, with 249 equal to approx .79)
......what was min drag speed?