Some stoves require just a little maintenance to keep them operating optimally. Liquid or multi-fuel stoves often feature a generator loop where liquid fuel is vaporised. This occasionally requires internal carbon deposits removing. It isn't a difficult task if carried out before it becomes a problem.
The whole point of a multi-fuel stove is that it gives you options. One fuel may be more suited to colder conditions, another may permit better simmering, one could be the cheapest option, another may be the only fuel available. Aspen 4 is amongst the very best of fuel options for a liquid fuel stove.
Three Points of the Compass 