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DON’T LET BAD DIESEL RUIN YOUR TRIP

The Unsealed 4X4 guide to diesel fuel filtration – and how to avoid contaminated fuel to begin with

We’ve all heard the horror stories about contaminated diesel causing $$$$ worth of damage, especially in common-rail diesel engines. And it’s not isolated to remote locations either; our local handyman had over $10,000 worth of damage caused to his D40 Navara filling up at a local Blue Mountains name-brand service station when water found it’s way into his fuel injection system. He ended up selling the car after it was repaired, and needless to say, he now shops elsewhere for his diesel. Here’s what we learnt after that experience, and hopefully we can all learn a few quick and easy lessons about protecting your vehicle and savings account from dodgy fuel.

WORDS BY EVAN SPENCE

GUIDE

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EF2000iS 2 kVA Inverter Generator

How do you know if your fuel is contaminated?
It’s rather easy to tell if diesel fuel is contaminated just by looking at it, but that’s not a reality or a possibility when refuelling, is it? According to the NRMA, there are four things to be aware of directly after refilling, if you think you may have a dodgy batch of dino-juice.

  • Is your engine running rough or lacking power?
  • Is the engine harder to start than usual?
  • Is your engine now misfiring, pinging or backfiring?
  • Is the check engine light now illuminated?

If you answered yes to any of these questions, stop driving the vehicle immediately and have it towed to a reputable mechanic for inspection; the longer you drive with contaminated fuel, the more damage you will do to your injection system and wallet. Make note of the time and date you filled up, and advise the fuel provider as soon as possible about the possibility of fuel contamination. This protects you, and potentially many other motorists.

What contaminants cause damage?
Water is by far the most common contaminant that will play havoc with your fuel injection system. Water introduces microbial growth, think fungus, mould and other bacteria, which leads to clogged filters from a sludge-like substance.

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What can go wrong?
If you are unlucky enough to pick up dodgy fuel, your entire fuel injection system, and ultimately engine, are at great risk of expensive damage. The fuel pump, lines connecting to the common rail, the actual common rail and injectors are the key components that will be affected, none of which are cheap or easy to repair. Due to high temperatures found in common-rail injection systems, water causes these components to rust, and rather quickly too. This rust works its way through the common-rail components, eventually causing injectors to seize – not a good time.

As fuel filters are not primarily designed to stop water – they are designed to stop particulates entering the fuel system – it’s a wise investment to look into aftermarket options that should stop water getting into your very expensive injection system. That’s easier said than done these days, so it’s time to explore some options out there, to see which form of contaminated fuel protection will work for your applications.

Water separator
As the name suggests, water separators are designed to remove water from fuel. This happens as water and diesel don’t weigh the same, thanks to centrifugal force, water is removed from the diesel and lands at the bottom of the separator in a clear bowl, providing a nice visual into the operation of the separator, and is easily drained out. Good quality units will be fitted with a sensor that will sound a buzzer or light letting you know water has entered the system; you can then drain this and, depending on the amount of water, keep driving or have the vehicle’s fuel system inspected to remove remaining contaminants. It is said that a quality water separator won’t restrict fuel flow over time, as it’s not a filter. But the other side of that coin is … they aren’t filters. If you are only worried about removing water from diesel, and not interested in filtering out foreign particles, a water separator will set you back roughly $70 - $140 for a kit, however some kits are also available with filters too, so it pays to do some window-shopping before spending your coin. Which leads us to additional fuel filters… 

Pre-filter vs post – let the debate begin
This is always a heated debate: pre- or post-auxiliary fuel filtration – which is best? What I want to do is just discuss the pros and cons of each, to help you make your mind up. Hey, any additional filtration is better than nothing in my eyes.

A pre-filter is installed between the vehicle’s fuel tank and original fuel filter, and the simplest way to think about it is this filter catches rocks, and the factory filter catches remaining pebbles. This is due to the different sized particles each filter is designed to trap, as such this could potentially lead to blockages of the aftermarket pre-filter, and reported restriction of flow. To be honest, I feel this is just the price of admission for fuel system protection in my eyes. Cary a spare, check/change it regularly and this is now a non-issue.

I’m going to make the call and say personally I run a diesel pre-filter kit in my HiLux, because I’d prefer to stop water and contaminants from entering the fuel system as early as possible, leaving the factory filtration system to do it’s job. You wouldn’t let a drunk punter into a pub then monitor them, you’d stop them from entering in the first place, if you get what I’m saying.

I also change my fuel filter every second oil change, roughly every 10,000km, with a genuine Toyota filter ($44 from Toyota, vs $25 aftermarket). This is cheap insurance basically. The Toyota filter in my case can filter to approximately four to five microns; a pre-filter will usually offer a 30-micron filter whereas a post-filter can go as low as two microns (extremely fine tolerances). A pre-filter will remove water and contaminants before reaching the factory filter, while providing nice clean diesel to the factory filter which can happily do its job still. Again, this is just my opinion and understanding on the matter. 

Fitment of a post-filter after the factory fuel filter means said factory fuel filter is still doing the lion’s share of hard work, as well as dealing with separating water. The post-filter has extremely fine tolerances as mentioned above, meaning the fuel that does come through has been really finely filtered, which is a positive. However I feel (again, my opinion) the factory fuel filter is capable of dealing with correct fuel filtration, a pre-filter with clear bowl to visually see if any water has entered the system, which is then easy to drain, and regular servicing is what I’d recommend.

  1. Always get a receipt, so you can prove when you filled up last. There are apps you can download to record these receipts so you don’t have to keep the paper copy. 
  2. Only fill up at busy reputable fuel stations if possible; if the servo looks old and dirty, who knows how old their tanks are?
  3. Avoid filling up after heavy rains or floods.
  4. Check to see if your insurance policy will cover contaminated fuel – it’s better than footing a big bill in the event the fuel provider won’t cover the contamination.
  5. Install additional aftermarket fuel filtration/water separation units.
  6. Look into a product called Mr Funnel – it’s a funnel that filters water out of fuel before putting it into your tank and costs under $50.
  7. If you see a fuel truck depositing fuel at a service station, find another one to fill up at.
  8. If you vehicle runs poorly after filling up, stop driving it immediately and have it towed to a reputable mechanic.
  9. Regularly change your fuel filter – it’s cheap insurance against particular contaminants.
  10. Avoid running your fuel tank too low often. I personally usually top up when the fuel gauge is a bit south of halfway – when possible.  

10 expert final tips

Check out our review of the Mr Funnel – does it actually work?

The Unsealed 4X4 guide to diesel fuel filtration – and how to avoid contaminated fuel to begin with

GUIDE

We’ve all heard the horror stories about contaminated diesel causing $$$$ worth of damage, especially in common-rail diesel engines. And it’s not isolated to remote locations either; our local handyman had over $10,000 worth of damage caused to his D40 Navara filling up at a local Blue Mountains name-brand service station when water found it’s way into his fuel injection system. He ended up selling the car after it was repaired, and needless to say, he now shops elsewhere for his diesel. Here’s what we learnt after that experience, and hopefully we can all learn a few quick and easy lessons about protecting your vehicle and savings account from dodgy fuel.

WORDS BY EVAN SPENCE

DON’T LET BAD DIESEL RUIN YOUR TRIP

SCROLL TO CONTINUE WITH CONTENT

ADVERTISEMENT

How do you know if your fuel is contaminated?
It’s rather easy to tell if diesel fuel is contaminated just by looking at it, but that’s not a reality or a possibility when refuelling, is it? According to the NRMA, there are four things to be aware of directly after refilling, if you think you may have a dodgy batch of dino-juice.

  • Is your engine running rough or lacking power?
  • Is the engine harder to start than usual?
  • Is your engine now misfiring, pinging or backfiring?
  • Is the check engine light now illuminated?

If you answered yes to any of these questions, stop driving the vehicle immediately and have it towed to a reputable mechanic for inspection; the longer you drive with contaminated fuel, the more damage you will do to your injection system and wallet. Make note of the time and date you filled up, and advise the fuel provider as soon as possible about the possibility of fuel contamination. This protects you, and potentially many other motorists.

What contaminants cause damage?
Water is by far the most common contaminant that will play havoc with your fuel injection system. Water introduces microbial growth, think fungus, mould and other bacteria, which leads to clogged filters from a sludge-like substance.

SCROLL TO CONTINUE WITH CONTENT

ADVERTISEMENT

What can go wrong?
If you are unlucky enough to pick up dodgy fuel, your entire fuel injection system, and ultimately engine, are at great risk of expensive damage. The fuel pump, lines connecting to the common rail, the actual common rail and injectors are the key components that will be affected, none of which are cheap or easy to repair. Due to high temperatures found in common-rail injection systems, water causes these components to rust, and rather quickly too. This rust works its way through the common-rail components, eventually causing injectors to seize – not a good time.

As fuel filters are not primarily designed to stop water – they are designed to stop particulates entering the fuel system – it’s a wise investment to look into aftermarket options that should stop water getting into your very expensive injection system. That’s easier said than done these days, so it’s time to explore some options out there, to see which form of contaminated fuel protection will work for your applications.

Water separator
As the name suggests, water separators are designed to remove water from fuel. This happens as water and diesel don’t weigh the same, thanks to centrifugal force, water is removed from the diesel and lands at the bottom of the separator in a clear bowl, providing a nice visual into the operation of the separator, and is easily drained out. Good quality units will be fitted with a sensor that will sound a buzzer or light letting you know water has entered the system; you can then drain this and, depending on the amount of water, keep driving or have the vehicle’s fuel system inspected to remove remaining contaminants. It is said that a quality water separator won’t restrict fuel flow over time, as it’s not a filter. But the other side of that coin is … they aren’t filters. If you are only worried about removing water from diesel, and not interested in filtering out foreign particles, a water separator will set you back roughly $70 - $140 for a kit, however some kits are also available with filters too, so it pays to do some window-shopping before spending your coin. Which leads us to additional fuel filters… 

Pre-filter vs post – let the debate begin
This is always a heated debate: pre- or post-auxiliary fuel filtration – which is best? What I want to do is just discuss the pros and cons of each, to help you make your mind up. Hey, any additional filtration is better than nothing in my eyes.

A pre-filter is installed between the vehicle’s fuel tank and original fuel filter, and the simplest way to think about it is this filter catches rocks, and the factory filter catches remaining pebbles. This is due to the different sized particles each filter is designed to trap, as such this could potentially lead to blockages of the aftermarket pre-filter, and reported restriction of flow. To be honest, I feel this is just the price of admission for fuel system protection in my eyes. Cary a spare, check/change it regularly and this is now a non-issue.

I’m going to make the call and say personally I run a diesel pre-filter kit in my HiLux, because I’d prefer to stop water and contaminants from entering the fuel system as early as possible, leaving the factory filtration system to do it’s job. You wouldn’t let a drunk punter into a pub then monitor them, you’d stop them from entering in the first place, if you get what I’m saying.

I also change my fuel filter every second oil change, roughly every 10,000km, with a genuine Toyota filter ($44 from Toyota, vs $25 aftermarket). This is cheap insurance basically. The Toyota filter in my case can filter to approximately four to five microns; a pre-filter will usually offer a 30-micron filter whereas a post-filter can go as low as two microns (extremely fine tolerances). A pre-filter will remove water and contaminants before reaching the factory filter, while providing nice clean diesel to the factory filter which can happily do its job still. Again, this is just my opinion and understanding on the matter. 

Fitment of a post-filter after the factory fuel filter means said factory fuel filter is still doing the lion’s share of hard work, as well as dealing with separating water. The post-filter has extremely fine tolerances as mentioned above, meaning the fuel that does come through has been really finely filtered, which is a positive. However I feel (again, my opinion) the factory fuel filter is capable of dealing with correct fuel filtration, a pre-filter with clear bowl to visually see if any water has entered the system, which is then easy to drain, and regular servicing is what I’d recommend.

  1. Always get a receipt, so you can prove when you filled up last. There are apps you can download to record these receipts so you don’t have to keep the paper copy. 
  2. Only fill up at busy reputable fuel stations if possible; if the servo looks old and dirty, who knows how old their tanks are?
  3. Avoid filling up after heavy rains or floods.
  4. Check to see if your insurance policy will cover contaminated fuel – it’s better than footing a big bill in the event the fuel provider won’t cover the contamination.
  5. Install additional aftermarket fuel filtration/water separation units.
  6. Look into a product called Mr Funnel – it’s a funnel that filters water out of fuel before putting it into your tank and costs under $50.
  7. If you see a fuel truck depositing fuel at a service station, find another one to fill up at.
  8. If you vehicle runs poorly after filling up, stop driving it immediately and have it towed to a reputable mechanic.
  9. Regularly change your fuel filter – it’s cheap insurance against particular contaminants.
  10. Avoid running your fuel tank too low often. I personally usually top up when the fuel gauge is a bit south of halfway – when possible.  

10 expert final tips

Check out our review of the Mr Funnel – does it actually work?