No matter what mix originally came in your backpacking canister, butane will have a lower vapor pressure. Butane is pretty safe to use for refilling.19 Jan 2012
How do you refill butane gas?
https://www.youtube.com/watch?v=JkC_dlO2UTo
Can you put butane back in the canister?
Yes the canister can be removed and used again.
Is it safe to refill gas canister?
Gas canisters can be very dangerous to refill if you aren't going about it the right way, and we want you to be as safe as possible. Overfilling should be avoided at all costs as the potential for the canister to leak or explode increases drastically.6 Feb 2017
Butane is pretty safe to use for refilling. Do NOT fill backpacking type canisters with 100% propane under any circumstances. The next step in refilling is to hook everything up.19 Jan 2012
Does Walmart sell refillable butane?
Purified Gas Butane Fuel for All Refillable Lighters (2 Pack) - Walmart.com.