Is Premium Diesel Worth It?

Don’t get into a dither on the forecourt anymore.

Once upon a time, diesel was diesel… and you didn’t have any real decisions to make when refilling the tank. Those were simpler times, when people didn’t buy jeans with holes already in them, or make drinks out of grass. But, time moves on.

These days, you have two options: regular diesel or premium diesel. Not dissimilar to petrol, right? Wrong. We did some research to find out what the go is.

One of the first things I came across in my research was this video from Pommy car show Fifth Gear. http://www.youtube.com/watch?v=ezjknhwcQXU?autoplay=1

But this doesn’t work for Australia necessarily. This is because in every country fuel is mixed and distilled to different standards and qualities. Once upon a time Australian diesel was pretty rough compared to Europe, and European manufacturers complained that they couldn’t introduce their leanest, cleanest and most efficient engines in Australia because of the fuel.

Since 2009 all Australian diesel is the ‘ultra-low sulphur’ kind, which means the fuel has only 10 parts-per-million (PPM) sulphur content. Ultra-low sulphur fuel means we can run cleaner and more efficient fuels, but the trade-off is the fuel has lower lubricity. To overcome this, ‘ULSD’ has additives thrown into the mix to help out.

Where petrol has octane, diesel has cetane. The cetane rating of a diesel indicates how big the ‘bang’ is; a higher number could give you an extra bump in performance.

It’s kind of easy to get fooled into thinking the ‘premium’ connotation in the more expensive diesels means they will give you more performance, but that isn’t really the case. In all cases (BP, Caltex and Shell), I found cetane ratings of regular and premium diesel were all the same. And there was little to no difference in lubricity levels or flash points.

The ‘premium’ aspect comes from the additives. More than just the additive to help with lubricity… and here are the important ones:

Detergents:

No, don’t whack a squirt of Dynamo or a spoon of Cold Power into your tank. Premium diesels have special detergents added that don’t affect the performance of the fuel, but will clean out deposits from your fuel injection system. The ridiculously fine nozzles of a modern injector are the most prone to partial blocking, but rails and pumps can all do with a bit of a clean.

Corrosion Inhibitors:

Some fuel tanks are made of steel, and plenty of your pipes, fittings, joiners and rails in the fuel system are made from a wide array of metals. Corrosion inhibitors are designed to help keep corrosion down, and all of those associated problems at bay.

Foaming Inhibitors:

I remember filling up a diesel bladder at Mt Dare, trying to get every drop into it before taking on the Madigan Line. I’d just had my last shower for 12 days, feeling resplendent in clean clothes that were meant to last 4-5 days. Then, a torrent of bubbling diesel spewed out of the bladder – covering me. Lesson learned.

Premium diesels have additives to stop the foaming, making it easier and cleaner to fill up your tank. Diesel didn’t always foam, but the addition of biodiesel into the mix is the culprit.

So, is it worth it?

Looking at the extra few cents per litre it costs you, compared to some extraordinary costs that fuel system parts cost under your bonnet, the premium diesel probably isn’t a bad idea. At least run a couple of tanks of the good stuff every now and then, to help clean the insides of your fuel system.

I would definitely look at running a few tanks of premium diesel after a long trip touring around and filling up at remote servos. Or, if you subject your diesel to lots of stop-start driving and short trips, premium can help to reduce (but not stop) the problems that come with it.

BP Premium Diesel

The specs:

Cetane Index: 46 minimum, 52 typical.

Flash Point (°C): 61.5 minimum, 66 normal.

Viscosity – kinematic @ 40°C:  2.0 to 4.5 range, 3.0 typical.

Lubricity wear scar diameter: 0.46 maximum, 0.40 typical.

Additives:

  • includes a lubricity additive
  • includes a detergent additive to clean fouled injectors
  • includes an additive to protect against corrosion
  • includes an additive to reduce foaming and splash back

Article from Unsealed 4×4

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Comments 10

  1. Great info. Where does the “Truck” diesel fit into this? Some stations have a couple of cents difference between truck and normal diesel.

  2. Good article thank you. I have a Landcruiser 1HZ and always wondered whether premium was doing anything positive in that old clunker. Presumably it is!

  3. Hi, It would have been good to see the other two specs, Shell and Caltex fuel, so we could the different between the fuels as I think there is a differentes, as i get better performance from different when towing

  4. Thank you very much on the diesel spex but what about diesel conditioners like diesel doctor ;; & diesel power ‘; Are thy worth it ?

  5. Hi, my name is Robert Ambrose an have a Nissan D40 !!! love it it runs beautifully.
    I have always added Diesel plus to my tank when refueling ??? What’s your thoughts on doing this.

    Cheers !!

  6. I’ve heard BP advertising premium diesel and after two tanks there is a noticeable difference so I thought I’d give it a try. So I started filling up at BP service station Princes Highway Little River only to find that I’d been filling up with standard type diesel. When I questioned the attendant their only reply was no its standard and they didn’t have premium grade. I would have thought that if you advertised premium grade fuel when you pulled in to a BP service station that’s what you’d be getting. I now fill up with Caltex premium Princes Highway Werribee.

  7. You only give stats on BP i find when i use Caltex i get 2 litres per 100 better per tank, i do not using BP. Although, sometimes in country areas there is foaming so i wonder what i am getting.

  8. Caltex, Shell and BP make my 105 series 1Hz go reallly well. I notice a drop in power level when I use servos that use Mobil fuel.

  9. G’day greg here, just put my first fill of premium in my 100 series and friggen thing is running like a dog. Put the foot down and virtually nothing not a happy camper. Any ideas or recommendations. Cheers

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