Alpine Diesel – Do you even need it?

Dex Fulton gives us the lowdown on alpine diesel, including what it is, why and when you need it, and what to do when you get caught out.

Winter is once again upon us, friends, and with it comes the inevitable trips to Australia’s alpine regions… and Tasmania… or anywhere that’s cold really. If you drive a petrol-powered vehicle, this means nothing beyond not forgetting your thermal undies and earmuffs. But for us diesel-driving folk, it means we’ll need to prepare for the potential damage to our fuel caused by cold temperatures. 

Essentially, sub-zero temps and dizzle don’t mix. It can vary a little depending on where you fuel up, but the general rule is that once the ambient is south of -3°C, the fuel in your tank, fuel lines, filter, fuel rail and anywhere else starts to gel up – it’s called the cloud point. Once the cloud point has been reached and your fuel resembles a bowl of porridge, it means your vehicle no worky no more. 

Why are you like this?!

The science behind diesel’s cloud point is, shockingly, pretty boring. It’s basically where the diesel liquid solution goes through a phase separation to form an emulsion. The paraffin wax in the fuel begins to solidify (causing a cloudy appearance, hence the name) which clogs up filters, injectors and anything that’s meant to have a liquid pass through it, not a gummy sort of sludge that resembles cake batter, but tastes much much worse (allegedly). 

Once your filter can no longer pass fuel through it, your lines are filled with a solidified wax and your injectors are trying to spray a fine mist of viscous sludge, your engine will run extremely poorly, if it even runs at all. 

Alpine diesel to the rescue

If you’ve ever been to a cold area of the country, you will have noticed the servos selling alpine diesel. Fuel companies like to be a bit secret squirrel over exactly what they blend with their regular diesel to concoct the alpine variant, but common consensus seems to be that a derivative of kerosene gets thrown in the vat, which lowers the cloud point by roughly 4°C, meaning your rig will be fine at temperatures reaching as low as -7°C. 

However, when you factor in extreme cold weather (the record is -23°C at Charlottes Pass), then you may need a little more anti-coagulant in your cocktail. This is where additives come into play, which you can buy in bottles from most highland servos. They can drop the cloud point of your diesel a further few degrees and hopefully keep things in their most-liquidy form. 

Depending on who you speak to, alpine diesel can purportedly damage modern diesel injection systems if used for a prolonged period of time, however we have seen no concrete evidence of this at the time of writing. 

Some alpine-area locals keep a 5L jerry of kerosene on hand in the back of the fourby in case the temperatures drop unexpectedly. It should be noted that of all of the people and businesses we spoke to, every single one was insistent that the ratio of kero to diesel not exceed 5%, and that a 3% kerosene mix would likely be more than enough to run in even the coldest areas of the country. BP recommends heating oil can be used at 25%, and kero at no more than 5%, just for reference.

Your car ain’t helping itself

One of the contributing factors to diesels gelling up is that pretty much all vehicles in this country are designed to keep temps as cool as possible and not retain heat. Obviously, in alpine areas, this can become counterproductive. Fuel coolers, which are basically ribbed alloy blocks on the fuel return line that are there to shed heat before the fuel gets back to the tank, are especially known for allowing the fuel to gum back up after it’s been heated by the engine. 

Wrapping your filter and cooler in rags (an old beanie is apparently the go here) and throwing some foam insulation over fuel lines is common winter prep for those who spend a lot of time in colder climates. 

For most of us who are just visiting, making sure your tank has at least 75% alpine diesel in it and maybe having a bottle of additive on hand if things get super chilly should be more than enough to see you away from trouble.

You’re stuck, now what?

It’s a bright morning in Hotham, you pile the fam into the Cruiser and aim to be on the slopes by 9 am. Only, the vehicle won’t start, or if it does it refuses to rev past 1000rpm and generally sounds like it’s just been diagnosed with emphysema. You remember forlornly that you forgot to fill up with alpine diesel.

Great. What now?

There’s a bunch of homebrew remedies for gummed-up diesels that range from the “huh, that’s pretty smart” to “yes, and how would sir prefer his face melted?” The main thing you’re trying to achieve here is to get your fuel system warmed up enough that the wax melts and your diesel returns to its natural liquid state so you can start it up. 

This can range from pouring warm water over the lines, filter and fuel rail to setting a fire under the fuel tank (no, seriously some folks do this). I’d like to think that it goes without saying that that fire one has a bright yellow sticker that says “hardcore do not recommend!” attached to it. 

The most common and effective remedy is to just wait. Usually, in this country, temps rarely stay below minus seven, so as the day warms up, your diesel will melt back into combustible fluid, and your vehicle will start up without a worry. Once it’s going and the engine comes up to operating temp, the residual heat from the block should provide enough to keep the fuel from gelling up.

So, do you need alpine diesel?

So, do you need alpine diesel? If you’re heading into below-freezing temps, particularly if you’re staying overnight, then yes, absolutely. If you live in Far-North Queensland and the coldest it ever gets is 25°C, then you’re probably right without it.