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 best of fuel options for a liquid fuel stove.
Every multi-fuel stove will only operate with certain types of fuels. Some stoves will burn a range of liquid fuels but not gas, or require jets changing first. Some fuel options are poor. Diesel can be difficult to get to burn well and can smoke badly. Paraffin, or kerosene, is a particularly mucky smelly fuel and this and other liquid fuels can clog up jets and generators etc with frustrating rapidity. Despite attempts made to clean it, a stove may never recover. Gas will be the cleanest option of all but is also one of the most expensive and can struggle in more extreme conditions. Some multi-fuel stoves will operate with unleaded petrol. But not all unleaded petrol is created equal.
Coleman Fuel, also known as White Gas, is a liquid petroleum fuel (100% light hydrotreated distillate), comprised of cyclohexane, nonane, octane, heptane and pentane with an octane rating of 50 to 55. The original white gas was an additive free petroleum distillate and is seldom found in that form now. The modern form of white gas, Coleman Fuel and other branded offerings such as MSR SuperFuel and Primus Power Fuel still contain various additives that inhibit rust, enable easier lighting and faster burning. While these are good fuels, they are expensive and may still clog stove components such as fuel lines and jets..
Unleaded petrol, a purer form of petroleum distillate, from the garage pump and used to fill the car, has many additives added to it and a multi-fuel stove would almost certainly operate better with a more specialised ‘cleaner’ fuel. There are a number of additive free alternatives to unleaded petrol, such as the aforementioned Coleman Fuel, and Three Points of the Compass has used this frequently with a Primus Omnifuel in the past with no problems but has now made the switch to cleaner burning Aspen 4 for both my Primus and Edelrid Hexon multi-fuel stoves with good results.
Roland Elmäng founded the Swedish Aspen company in 1988 on the shores of Lake Aspen when he read an article in Skogen about the problems faced by Swedish forest workers exposed to exhaust fumes from chainsaws and brushcutters. With the introduction of the alkylate fuel, this not only improved the working conditions of the forestry workers but also meant their petrol driven machines operated better too.
The fuel is distributed in the UK by the Poole based Anglo American Oil Company who specialise in fuel and oil products. This family business was founded in 1999 by Swede Anders Hildebrand, who knew of Aspen fuel from his home country and became the UK distributor to over 350 retailers. Stockists can be found here. Aspen 4 is most easily available in one and five litre plastic containers. Few of us are going to be tracking down the 25 and 200 litre containers.
“can be stored for 3 – 5 years without any deterioration in quality“Aspen
Aspen 4 is alkylate fuel without added oil. It is sold for use with petrol lawnmowers, rotary cultivators, strimmers, boat engines and other 4-stroke engines. It is not suitable for use with 2-stroke engines unless oil is added first to the appropriate ratio. Aspen 2 comes in red containers, contains 2% synthetic oil and is for 2-stroke engines. Aspen 2 is not suitable for use with multi-fuel stoves. Aspen 4 comes in blue containers, does not contain synthetic oil and is suitable for use with multi-fuel stoves. Do not attempt to use Aspen D, which is for Diesel engines.
Because Aspen fuel has no ethanol it is hygroscopic/chemically inert, so does not attract moisture or water vapour. So not only is it suited for use in a marine environment but also for storage as it will not deteriorate with time. Aspen 4 has a lifespan of approximately 10 times that of regular petrol and can be left from season to season. This is one of the reasons why Three Points of the Compass now uses this fuel in the petrol lawn mower. It can be left with fuel in the tank over winter and the mower will still fire up in the spring.
Aspen 4 is made from the gases from the top of the distillation tower. These are then synthetically modified into a liquid again. It is almost completely free from harmful substances such as sulphur, benzene, aromatic hydrocarbons or olefins. Aspen has virtually no aromatic compounds. These compounds, found in normal petrol distillates, are highly toxic and even small amounts caused by incomplete burning will frequently cause nausea and headaches. Aspen 4 burns cleaner with less or no smell. The Aspen 4 data sheet is long and informative and can be seen here.
Because the fuel contains no unsaturated hydrocarbons there is no build up of resins in stove jets. While it is obviously still a fossil fuel, it is a cleaner fuel. While ordinary pump petrol is classified as toxic, alkylate petrol is classified as hazardous. That said, it is still an irritant and the usual care taken when handling it.
Availability of alkylate petrol is limited because the actual alkylation process to produce Aspen is an advanced and expensive process which only a few refineries in the world can complete. Therefore Aspen 4 is a great deal more expensive than the petrol going in the car, though it is cheaper per litre than Coleman Fuel. But multi-fuel stoves aren’t cheap either. Anything that prolongs the life of a stove and also keeps it working when it needs to, deserves serious consideration. The fuel can also be used with camping lanterns that burn white gas with the same benefits.