Cziffra's fingering in HR 6 octaves

[rohansahai]

I just saw the video ...... seemed to me that he was not using 1-5 ...but 1-4 as well..maybe even 1-3  in the repeated octaves. Any comments on how this might help ? Speed?

[faulty_damper]

1-5 on white tops
1-4 on black tops after 1-5 on white tops
1-5 on white tops after 1-4 on black tops.

This should be common practice of how to navigate octaves if your hands are big enough.  See Chopin Study Opus 25 No. 10.  1-4 on black tops can reduce the distance you have to move your hand after you have played white tops with 1-5.

I find 1-4 and 1-3 on black keys uncomfortable as it forces the wrist in an uncomfortable bend.  For longer passages, like the study, it may be necessary to avoid extended 1-5 which can cause strain on the hand.

Cziffra had large hands.

[m]

I just saw the video ...... seemed to me that he was not using 1-5 ...but 1-4 as well..maybe even 1-3  in the repeated octaves. Any comments on how this might help ? Speed?

Yes, your observation is absolutely right! He uses ingenious trick, playing repeated octaves in both HR6 and Schumann Toccata middle part with alternating 1/5-1/4.

I play both pieces and this fingering results in much faster and lighter execution.

Needless to say, it never came up to my mind until I saw that video, first.
I guess, one has to have big enough hands to be able to do it.