Using revolving credit to make lump sum mortgage repayment.

We have a revolving credit of $50k currently fully paid at $0 balance.

I am keen to pay down our mortgage as fast as possible.

Does it make sense to take a chunk of the RC funds (eg. $20K, keeping under the 5% per year limit ANZ set so as not to incur repayment fees) and make a lump sum payment on our mortgage?

I would then allocate a portion of income to minimise the $20k lump sum paid over the next year or two.

Or do the higher floating interest rates paid on the $20k taken out of the RC facility make this a pointless exercise? Am I better to save up for a year or two and then put a lump sum down without dipping into the RC facility?

EDIT:

Thanks to all those who contributed. I hadn't considered increasing the RC and reducing one of my fixed loans when it breaks in late March. This inspired a new idea. As I am a contractor I hold all the money earmarked for tax repayments in a saver account.

The new idea is to increase the RC as above, and send the funds earmarked for tax to the RC on a fortnightly basis instead of savings account. I will miss out on 3.85% interest in savings but using ChatGPT for the calculations I found that I will still be better off by doing this (by $1300pa).

However it is useful to note that beyond a certain RC increase (for me, $40K), the interest saved starts to fall because of the opportunity cost from missed interest in savings as well as the higher RC rate chewing into the interest saved from the fixed loan reduction.