The classic fuel contamination symptoms are rough idling, sputtering, loss of power, hard starting, and a check engine light soon after a fill up. If your car ran fine before you filled up and started playing up within a few minutes of leaving the servo, bad fuel is a real suspect. Don't panic. Most contaminated fuel problems are fixed on the spot with a drain and flush. No tow, no workshop queue.
The 8 fuel contamination symptoms to check
- 1. Hard starting or no start straight after a fill up
- 2. Rough idle. The car shakes or feels lumpy at the lights
- 3. Sputtering or misfiring when you accelerate
- 4. Loss of power, especially uphill or when overtaking
- 5. Check engine light that appears right after refuelling
- 6. Unusual smoke from the exhaust
- 7. Stalling. It stalls, restarts, then stalls again
- 8. Ran fine, then died a few kilometres down the road
The timing is the giveaway. Any of these on their own can have other causes. Any of these within minutes of a fill up points straight at the fuel. If the car won't start at all, our guide on a car that won't start after a fill up walks through that exact situation. And if it ran fine at first then died later, that pattern has its own guide.
Bad fuel or wrong fuel? How to tell the difference
Two different problems, same roadside fix.
- Wrong fuel means the wrong nozzle went in. Petrol in a diesel, diesel in a petrol. If there's any chance that happened, check the wrong fuel symptoms and stop driving.
- Contaminated fuel means the right fuel went in, but it came with something extra. Water, dirt, rust, or fuel that sat in the servo's tank too long.
You don't need to be sure which one you have. The fix is the same either way. Drain the tank, flush the lines, refuel with clean fuel. That's the whole job, done where you're parked.
What actually gets into the fuel
Contamination isn't mysterious. It's almost always one of these:
- Water. Condensation in tanks, or water getting into a servo's underground storage. Water and fuel don't mix, and your engine notices fast. Here's what happens when water gets in a fuel tank.
- Dirt, rust and sediment. It settles at the bottom of storage tanks and gets stirred up when tanks run low.
- Stale fuel. Petrol degrades over months. Old fuel burns poorly and gums things up.
What to do if you think you got bad fuel
- Stop driving as soon as it's safe. The longer the engine runs, the deeper the contamination spreads into the lines, filter, and injectors.
- Record where you filled up. Servo, pump number, time. Take a photo of the receipt. You may need it for a claim.
- Don't keep cranking a no-start. Repeated cranking just pulls more bad fuel through the system.
- Call a mobile fuel drain. The tank gets drained, the lines flushed, and clean fuel goes in, all where you're parked.
If the servo's fuel caused the problem, you may not be the one who ends up paying. Our guide on who pays when the servo is at fault covers the evidence to keep and how claims work.
The Bottom Line
Rough running, sputtering, power loss, or a no-start right after a fill up usually means something is wrong with the fuel, not the car. Stop driving, keep your receipt, and get the tank drained where you're parked. Wrong fuel happens to anyone, and bad fuel isn't your fault at all. We come to you, 24/7 across Perth.
