I asked this question Why did car go quiter and cut out after fuel change? and somebody mentioned in the comments that I may have used watered down gas. This seems plausible and I did think the fuel seemed a bit watery as some of it sprayed near the fuel cap.

The comment said I should just add normal fuel and run the car problem will go away however a quick internet search says the water may have damaged filters etc.

Should I just add more fuel and run or is there anything else I should be aware of/might anything have got damaged?


Water does not mix with pure gasoline, and is heavier than fuel so it will sink to the bottom of the tank. Ethanol is hygroscopic, meaning it will mix with water, so if you have an ethanol blend with a small amount of water contamination it will likely have disappeared, if there is a lot of contamination some of the water will be absorbed by the fuel and the rest will drop to the bottom of the tank.

The bottom of the tank is where the fuel is pumped from, so if you have a lot of water there it's that which will get pumped into your fuel lines and your car engine will stop running. Having your engine full of water is bad. If your fuel is part ethanol and it's absorbed water that's not quite as bad, the engine may still run but it may be rough and stall. Either way you want to drain the system and fuel lines, then fill with good fuel. You do not want to keep cranking it if there's water in the lines as you could damage your engine your engine and cause a much worse problem.

| improve this answer | |
  • 2
    Hydro-lock usually happens when water enters the cylinders via the air intake... At least in the cases I have dealt with... The amount coming in via the fuel system is too small... – Solar Mike Jan 18 '19 at 9:08
  • Fair point @SolarMike, it can still cause damage, I will edit to make that clear. – GdD Jan 18 '19 at 9:33
  • mostly it can only cause things like rust, if you get the engine running that will dry it out and prevent any damage – Jasen Jan 19 '19 at 6:02

Whilst I completely understand that this isn't a shopping advice site, have you considered adding a fresh tank of fuel (from a different fuel station) along with a fuel system dryer additive. One product (of probably a number) you might consider is Wynns Dry Fuel, you add it to the tank and it's specifically designed to remove water. Added bonus is that it cleans the fuel system in the process of removing the water.

Of course every tank of fuel you add will effectively reduce the quantity of water in the system as it will effectively dilute it BUT remember that, without any additive, the majority of the water will "pool" under the fuel in the tank.

| improve this answer | |
  • sorry steve, if it dilutes with every fuel change then doesn't that mean it will just go over time and so unless u want it gone quicker, u dont have to use the additive? have i understood you correctly? – James Wilson Jan 18 '19 at 23:31
  • It will become progressively less and less so effectively becomes less and less of a problem. As with any contamination, adding fresh liquid will go a significant way towards eradicating the contamination. Each tank fill dilutes the contaminant a little more. – Steve Matthews Jan 18 '19 at 23:35
  • or just add ethanol (the cheap denatured alcohol) – Jasen Jan 19 '19 at 6:03

Well, once you have identified the supplier, then avoid buying from there.

You could fit a water trap aka sedimenter which may or may not have a transparent section to allow a visual inspection for any water. Make sure it will support the pressure in that part of the system.

For now, drain the poor fuel out and also all the pipes and refill with known good fuel.

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.