I'm booking an ex-HKG DCIR22 and in an effort to get an idea of the difference in fuel surcharges from booking a flight under one code or another, I've used the on-line tool to price some DONE3s that include the target flight from the DCIR22.

(For example, to compare booking the same SYD-LAX flight as either QF11 or AA7362, I set up a DONE4 that included SYD-LAX and priced it both ways.)

SYD-LAX QF vs AA: $175 less booking AA.
LAX-SYD QF vs AA: $724 less booking QF.
DFW-NRT JL vs AA: $20 less booking JL.
HKG-LAX CX vs AA: $157 less booking AA.
LHR-JNB BA vs AA: $318 less booking AA.
LAX-LHR IB vs AA: $542 less booking AA.

I was really shocked just looking at QF vs AA, it was so $724 more for AA in one direction but $175 more for AA in the other direction.

Edited: Corrected SYD-LAX is cheaper on AA than QF (but LAX-SYD is cheaper on QF)