Lyn: if we assume CCP applies a stacking penalty of sorts to the AB and Fuel Conservation skills where one skill uses the modified value of the module as its base rather than just adding one bonus to the other and then applying that to the module's base value, then yes. If they don't, we're going to end up with afterburners that use zero cap per cycle, because Fuel Conservation already gives a 50% reduction in AB cap use per cycle at level 5.
Assuming both skills at level 4, and an AB with a 10 second base cycle duration and 10GJ/cycle cap use:
- Current skills: (10GJ * 60%) / (10s * 140%) = 6GJ/14s = 3/7 GJ/s.
- Supposed changes: ((10GJ * 60%) * 60%) / (10s * 80%) = 3.6/8s = .45 GJ/s
Both skills at 5:
- Current: (10GJ * 50%) / (10s * 150%) = 5GJ/15s = 1/3 GJ/s
- Supposed: ((10GJ * 50%) * 50%) / (10s * 75%) = 2.5GJ/7.5s = 1/3 GJ/s
So it'll be no effective change in cap use over time if both skills are at 5 and they use that kind of math, but only if they use that specific bonus stacking method. I don't think it'll be the same for any other combination of the skills after a change to that set of bonuses.
Knowing CCP, however, it will probably not be that simple.