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What Diesel Should I Use?

Recently, we discussed the differences between grades of petrol fuel commonly sold for road-use in Australia. The short version being that higher grades of fuel are generally for higher performance engines or vehicles with certain emissions control equipment.

But when it comes to diesel vehicles, there are often just one or two choices at most fuel stations that are suitable for your vehicle.

If you’re impatient and just want the short version, there’s only one grade of diesel base fuel sold in Australia, so it generally doesn’t matter what pump you go to. The in-depth answer is a little more involved.

Standard Diesel

All types of petrol and diesel are refined from the same crude oil, just the methods and temperatures of refinement result in vastly different end products, and unlike petrol, with its different RON or Octane grades. Diesel is just all collectively sold under a single grade of ‘Diesel’.

That being said, diesel fuel *can* have differing quality, and this is measured with a ‘Cetane’ rating. Cetane is a measurement of how quickly and completely diesel fuel burns, with higher cetane numbers meaning a more efficient and complete burn.

While RON and Octane is a measurement and indication of a fuels’ ability to avoid damaging premature ignition, Cetane is a measurement of a diesel fuel’s ability to ignite as soon as possible, with faster being better in the case of diesel engines.

All diesel fuel sold in Australia meets or exceeds a Cetane rating of 46, with higher Cetane ratings available through additives.

The simple answer to the question of ‘what diesel should I use?’ is ‘any’ and that the base used for all diesel in Australia is the same blend and will run the same, regardless of what vehicle you drive. The difference is in additive packages that are put into the fuel.

Winter Diesel

Because of diesels’ chemical make up, it is much more susceptible to partially freezing, or gelling in extremely cold conditions. So in alpine regions where temperatures are known to drop to -10c or lower, it’s not unheard of for a special blend of diesel to be sold. This is generally just sold out of the standard bowser and you’re unlikely to see any special labeling or signage.

Obviously, in Australia, finding temperatures that low isn’t very common, so you’re unlikely to find winter diesel. Still, it’s worth mentioning in case you happen to travel internationally, or you’re roadtripping in Tasmania during winter and still have your mainland diesel in your tank.

You can also purchase additives to add to your fuel tank that give you the same benefits as winter diesel, in case you’re heading somewhere extremely cold but you already have a full tank of fuel.

Truck diesel

You’re not missing out on anything by not using a bowser marked as ‘truck diesel’. Truck diesel bowsers dispense standard diesel, but the difference is the pump flow rates and the nozzle size. Standing around while topping up your 60 litre tank on your car is one thing, but waiting around while you fill up 300 to 500 litres of diesel when you’re supposed to be on the road, working, is another.

It’s ill-advised to try your luck and use a truck bowser on your car or SUV as the high flow of fuel can often overpower your filler system, resulting in fuel spilling over your vehicle, yourself and the fuel station yard. An embarrassing and potentially expensive mistake.

Premium Diesel

Inside diesel engines, the fuel is sprayed directly into the combustion chamber by ultra high pressure injectors that function at pressures higher than 20,000psi. If there is any contamination or build up inside the fuel system or injectors, you’ll experience rough running, poor economy and reduced performance.

With this in mind, many of the large fuel station chains will also stock something called ‘Premium Diesel’. Unlike premium petrols, premium diesels are the same grade of diesel fuel as the other bowser, but often contain additives designed to assist with engine cleaning, performance and maintenance.

Premium diesel is just regular diesel with fuel system cleaning additives that help prevent, or reduce, build ups of contaminants in your fuel system, and we typically recommend putting a tank of premium diesel into your vehicle every few months, at least, to keep things running smoothly.

Different companies will market this premium diesel differently, with names such as ‘Premium Diesel’, ‘Ultimate Diesel’, ‘Techron Diesel’ and more. Each company has their own secret herbs and spices for additives but the goal is the same.

Other Bowsers for Diesel Vehicles

You might find other bowsers at your fuel station that sell product for your vehicle too.

Bio-Diesel

Unlike traditional diesel fuels that are a result of processed crude oils, biodiesel is refined from a base made from vegetable oils, animal fat or cooking oil. Australian regulations allow for biodiesel to be added to your standard bowser in up to 5% quantities by volume without any extra labelling. Higher blends of biodiesel and petroleum diesel can be sold, with B5 and B20 (for % of biodiesel) the most common variants.

Elsewhere in the world, a product called renewable diesel is available which is able to take a much wider variety of feedstocks, but Renewable Diesel hasn’t really taken off in Australia, as of writing.

DEF

DEF stands for Diesel Exhaust Fluid with AdBlue being a product name for a particular brand of diesel exhaust fluid. Before we get too far into this section, we have to make it clear. DEF of any kind is NOT fuel and absolutely should not be added to your fuel tank under any circumstances. Adblue/DEF fluid/urea is highly corrosive and will cause many thousands of dollars of damage, should it be added into your fuel tank and the engine is then started.

DEF is used in vehicles to reduce emissions. This fluid is sprayed into the exhaust of vehicles and helps convert oxides of nitrogen into harmless gas and water vapour. DEF is usually available either at a dedicated bowser, or in packaged bottles at service stations.

Off-road Diesel

While you’re unlikely to find off-road diesel at a fuel station, there’s a possibility you’ll come across it in rural areas in some parts of the country. So called ‘ag diesel’ or ‘off-road diesel’ is the same stuff you’ll find in a normal bowser, but it’s often dyed a bright colour and is taxed differently due to being specifically sold for non-road use vehicles such as farm equipment, generators, tractors, excavation equipment and more. You risk huge fines if you’re caught driving your diesel vehicle with off-road diesel in the tank.

Does It Matter Which Diesel You Use?

From a simply mechanical standpoint, no. All diesel fuels meet or exceed the government-mandated Cetane rating of 46 and will result in the same level of power and economy.

Unlike petrol, there aren’t multiple ‘grades’ of diesel for consumers to worry about, but you may find improvements in cold climates or on older, high mileage engines depending on the additives that are in the fuel you use.

For any of your fuel system related questions, servicing, inspections and repairs, you’d better speak to the expert team at Donnellans.

With 4 convenient locations across the Greater South Eastern Melbourne Region, we can help you with all of your tyre, wheel and mechanical servicing needs. Find your local store below: