beware sfc!
Beware beware. GE quote thrust specific fuel consumption on their lie-sheets for sea-level ISA takeoff conditions. Most everybody else will quote for a cruise Mach No and Flight Level.
Thus a GE lie-sheet might say 0.33lb/lb-hr whilst RR quote say 0.57 but if the actual reference conditions are omitted comparison is not only odious but as much use as a chocolate teapot.
If I had a dollar for every bean-counter (and sometimes a pilot) who says "Why don't we fit GE, they consume nearly half as much as a Roller?" I'd be a rich man.
The GE in good nick on my biggie just before I retired was doing 0.587lb/lb-hr at best cruise, opening out to 0.603lb/lb-hr when a tad "off-axis". I derived these figs from aerodynamic data gleaned over the years and courses in Seattle and working back from fuel flow figs.
When looking at figures it is a case of apples v. oranges and caveat emptor.
Best Rgds
The E