Symptoms
- Symptoms start shortly after filling up
- Rough idle, stalling, or hesitation
- Check engine light with a misfire or fuel-related code
- Possible sputtering at higher speeds
Likely causes
- PossibleWater contamination in the fuelWater can get into underground station tanks and doesn't burn properly in the engine.
- PossibleDebris or sediment in the fuelRust or sediment stirred up in a tank can clog filters and injectors.
- PossibleOld or stale fuel (long-parked vehicle)Gasoline degrades over months, especially with ethanol blends, and can cause poor combustion.
- Less commonWrong fuel grade or type accidentally usedUsing diesel in a gas engine or vice versa causes severe, immediate problems rather than mild ones.
What to do
- If you suspect you just put in the wrong fuel type entirely (like diesel in a gas car), do not start the engine; have it towed and the tank drained instead.
- For suspected bad gas, avoid driving further than necessary and consider adding a fresh, larger amount of good fuel to dilute the bad batch if you must drive.
- Note the date, time, and station of the fill-up in case you need to report it or seek reimbursement.
- Have a shop check and replace the fuel filter, since it likely caught much of the contamination.
- Have the fuel system inspected if problems continue after a filter change and a fresh tank of fuel.
- Consider a fuel system cleaning service if performance doesn't fully recover after a filter change.
Tools and parts
Fuel filterSearch: “fuel filter for [year make model]”
Fuel system cleaner (fuel-injected gas engines)Search: “fuel injector cleaner additive”
When to call a pro
If you suspect the wrong fuel type entirely, don't start the car; call for a tow and have the tank professionally drained and flushed.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.