Andy says that although there is no perfect refrigerant, propane has a lot to offer. Propane scores very highly in all criteria bar one. It has a suitable pressure-temperature relationship (very similar to R-22); it has a relatively high latent heat but a low index of compression; it is cheap and readily available, and it is compatible with mineral oils - not a surprise as it is a kind of mineral oil itself! Environmentally, it also performs well, having no effect on the ozone layer and a very low global warming potential - even lower than the HFOs.