Manufacturers that once supplied MAPP gas, which has been discontinued, are now pushing propylene fuel. It has many of the same attributes as MAPP gas, including a higher price tag. However, that cost buys you greater performance.
• Has a flame temperature in air of roughly 3600°F, so it can be used to braze metal
• Burns hot enough to overcome the thermal effects of small amounts of water in plumbing lines, making it great for remodeling tasks
• Heats pipe and fittings 20% to 24% faster than propane, decreasing overall labor time
• Suitable for soldering or brazing pipe 1/8 in. to 3 in. in dia.
• Less forgiving than propane in terms of safety and technique
$9 per 16.92-oz. cylinder