Maintaining and servicing a vehicle is not always enough to keep it safe. Sometimes contaminated fuel gets in the way and damages the fuel systems of our beloved vehicles without us knowing it before it gets too late. What is contaminated fuel, where does it come from and how to avoid it?
What is Contaminated Fuel?
As opposed to clean fuel, contaminated fuel is full of build-up microbial growth (the so-called diesel bugs) or water and looks non-homogenous. Microbes that feed on your fuel also excrement regularly as a by-product of them feeding and further contaminate the fuel which might end up severely damaging the fuel pump, fuel injectors or the filtration system of your vehicles.
We get contaminated fuel from service stations when filling up our fuel tanks with fuel from the station’s bottom of the tank. (Note: Putting the wrong fuel in your car, like petrol in a diesel engine, is an equally common and damaging form of ‘contamination’ that affects thousands of Australian drivers each year).
Is Fuel Contamination Common in Australia?
While Australian fuel quality is strictly regulated by the Fuel Quality Standards Act 2000, issues still occur. In December 2025, Australia fully adopted ultra-low sulfur petrol standards (10ppm), bringing us in line with global best practices.
However, issues at the pump still make headlines. In September 2025, multiple drivers in Melbourne’s east were left stranded and facing major repair bills after a service station dispensed contaminated petrol. Furthermore, in February 2026, the ACCC secured a $16 million Federal Court penalty against Mobil Oil Australia for making false and misleading claims about the quality of fuel sold at nine Queensland service stations over a four-year period.
While this was a case of misleading advertising rather than physical contamination, it highlights the importance of consumer vigilance at the pump.
How Much Does Contaminated Fuel Cost to Fix?
If you realise you have contaminated fuel (or the wrong fuel) before starting the engine, mobile drainage services in Australia typically cost a few hundred dollars. However, if you start the engine, the costs skyrocket:
- Fuel pump replacement: $500 – $1,500+
- Fuel injector replacement: $500 – $2,500 per injector
- Complete engine rebuild: $5,000 – $20,000+ (worst-case scenario for modern common-rail diesels)
How to Spot Fuel Contamination Symptoms
If you notice that your petrol or diesel engine starts rougher than usual or lacks performance or power, there might be an issue with your fuel system. If you are experiencing any backfiring, pinging or misfiring, contaminated fuel could also be the case.
If you spot any corrosion on your fuel tank it’s time to go to the mechanic, as you might have driven on badly contaminated fuel for quite some time. You can always check the fuel by sipping it in a glass. Clean diesel looks transparent with a yellowish colour with no sludge, whereas contaminated one with rust, diesel bugs or water would have sludge and be dirty and slimy to the look. You won’t be able to look through it.
Modern common rail diesel injectors are very susceptible to damage from larger solid particles, thus making sure you are driving with the right fuel is important. Don’t most vehicles have fuel filters, don’t they help?
What to Do If You Suspect Contaminated or Wrong Fuel
If you realise you’ve pumped contaminated fuel or the wrong fuel (e.g., petrol in a diesel car):
1. Do not start the engine: If you haven’t turned the key, don’t. This keeps the contamination in the tank and out of the engine.
2. Call roadside assistance: Contact a mobile wrong-fuel rescue service or your motoring club (NRMA, RACV, RACQ, etc.) to drain and flush the tank.
3. Keep your receipt: You will need proof of purchase to make any claims.
4. Get it in writing: Ask your mechanic for a written report confirming the damage was caused by contaminated fuel.
Your Consumer Rights
Under Australian Consumer Law (ACL), fuel is considered a ‘good’ and must be of acceptable quality. If a service station sells you contaminated fuel, or an attendant pumps the wrong fuel into your car, Consumer Affairs Victoria and other state bodies advise that you are entitled to a refund and compensation for the resulting mechanical repairs. You should send a formal letter of demand to the retailer and can escalate the issue to your state’s civil tribunal (e.g., VCAT, NCAT) if they refuse to pay.
Do Fuel Filters Help Against Fuel Contamination?
Most fuel systems have fuel filters. Most fuel filters serve the purpose to protect fuel dispensers in service stations and not your vehicle as much. Most fuel filters are netted up to 10 microns which filters only the rust up to 10 microns and nothing else. All other fuel contamination gets into the fuel system of your vehicle.
The damage on your vehicle depends on the contaminants in the fuel. 90% of fuel consumers rarely have a problem because they rarely have the misfortune to fill up their storage tanks with fuel that has been laying in the bottom of the fuel tank of the gas station, where most of the rust, water and diesel bugs lurk.
Nevertheless, 10% is quite a lot and sounds like Russian roulette. Newer vehicles are at higher risk since older vehicles and trucks are equipped with rotary fuel pumps that are quite bulletproof. Newer fuel pumps, on the other hand, are quite vulnerable to small pieces of solid material.
How to Avoid Diesel Fuel Contamination
It doesn’t matter if you are refuelling in a brand new fuel line or a used-up gas station. Water contamination, diesel bugs and rust add up everywhere and are very hard to avoid, especially if you are refuelling just after the fuel has arrived. Preventative measures should be taken to avoid large amounts of contaminated fuel supply for your vehicle.
Avoid filling up your fuel tanks after there was a fuel delivery and or a resupply on the gas station. The main reason for that is that when the new fuel gets pumped into the service station’s fuel tank, it presses up some of the sludge from the bottom of the tank and it might get into your car’s system.
If you know for certain that your fuel tank has been contaminated there are a few solutions you might decide to follow in order to get it back to life. The simplest one is picking the right fuel additive and using it on a regular basis to keep away the diesel bugs and water from your tank.
On the other hand, if your fuel tank has been heavily contaminated, you might also need to clean it entirely, before sipping in any fuel additives. Clean the storage tank by emptying it and deep cleaning it with the help of a mechanic. Include all filters and lines of the tank during the cleaning. Scrape off any sludge, residue, asphaltenes, as well as sediment from the bottom of the tank.
Mechanics will let you know whether your tank needs replacing or it can be fixed right away. If it’s beyond help, do not hesitate and replace it before it causes further damage to the engine of your vehicle.
Does Fuel Doctor Actually Work?
Fuel Doctor disperses the moisture in the system from sub-micronic level and allows your fuel to burn safely. Moreover, the fungal diesel bugs derive its oxygen from the water in your fuel. If there is no water, there is no oxygen and the diesel bugs die.
Fuel Doctor breaks down the fungus and the rust into microscopic particles in seconds and allows your fuel system to function safely, free from corrosion and diesel bugs.
A simple test was performed to show how just a few drops of the fuel additive disperses the unwanted substances from your fuel in just seconds.
Before Fuel Doctor:
Fuel Doctor was developed by chemists to preserve their own fuel and prevent fuel contamination. Later on, it became a business since the need for it in the marked awoke.
After Fuel Doctor:
As you can clearly see in the images above, Fuel Doctor cleanses the fuel right away with extraordinary efficiency.
How to use the Fuel Doctor Fuel Additive
One litre of Fuel Doctor per 100 litres of tank capacity is enough to completely cleanse your tank in the beginning. Doesn’t matter whether your vehicle has a diesel engine or a petrol one, neither whether you are using biodiesel or a standard one. Basic instructions are available on the back of the packaging. Later on, just a ml of the fuel additive per litre of fuel is enough to keep the bugs and rust away as servicing.
You can’t hurt your tank with Fuel Doctor even if you overdose your system on it. A case study with an Australian fleet shows how they haven’t changed a single pump or injector in 60 million kilometres and 24 years. This exceptional fuel additive is an example of good chemistry at its finest.
Not only does using fuel additive improve the health of your vehicle but in some cases, it might also lower the emissions and increase the amount of time your oil will last.
Avoid Fuel Contamination Once and for All
Paying just a few extra bucks per tank for a fuel additive, in order to ensure the safety of your fuel system, fuel filters, and prevent rust from piling up into your fuel tank, is more than worth it. It’s a small investment that might end up saving you thousands of dollars in terms of repairs and servicing.
Fuel Doctor Australia is our preferred choice of fuel additive but there are also others that you might consider using. If you are uncertain what to do, and your fuel has been contaminated, better visit a licensed mechanic and ask for help before it gets too late for your vehicle.
