IMHO
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I would use the new one if you don’t want to degrease the old one. Thou if you take off the old one, it doesn’t take more than a few minutes to clean with some simple green or purple power degreaser and a scrubber, also get those jockey wheels. If you don’t clean them you will find your wax on your chain gets a dirty black/grey greasy look to it. The effort you put in now, will make not having to clean them in the future, they stay pretty clean going forward.
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Used Gulf wax for a couple years - works great. Trying Molten Speed Wax currently out of curiosity. Gulf wax is cheap and can be found relatively easily.