I have overfilled or "top off" my fuel tank

[Battousai1]

Hi guys, I just had a brand new Hyundai vehicle and it is a gasoline one, I had it since 3 days ago.

I made a mistake by not "quickly" reading the owner's manual first specifically the first few pages concerning information about the gasoline to use and break-in instruction.

So from the dealer I went to straight to the gasoline station to put in some fuel and the very first mistake I did was to to "top off" the fuel tank. This is my first brand new gasoline vehicle and all of the vehicles I had are diesel engine vehicles. I just realized after reading and watching videos on Youtube that topping off is dangerous and will damage your "EVAP" system.

The amount of excess fuel I topped off was around 4-5 liters, the fuel tank capacity of my vehicle is 40 liters and I have topped it off at around 45 liters. Although I have not topped it off up to the brim.

After learning that we should not top off our fuel tanks, this will be the first (for gas) and last time that I will top-off the fuel tank.

Now, my question is, is the EVAP system of my brand new vehicle already compromised? Should I bring it to the service center and have the charcoal canister replaced?

[Arika]

can you explain how you did this?

Any gas station pump has an auto cutoff when the tank is "full", how did you fill it beyond that point?

[Battousai1]

Just now, Arika S said:

can you explain how you did this?

Any gas station pump has an auto cutoff when the tank is "full", how did you fill it beyond that point?

Basically, you just put more gas after the auto cutoff until you see the gasoline near the brim.

[HenrySalayne]

I don't think you can really do any harm to the EVAP system, even when fuel is already coming out the filling port.

The "cut-off" from the petrol station is back-flow controlled. It's not an "exact" measurement in any way. Higher flow rates will trigger it sooner.

 

[starsmine]

36 minutes ago, Battousai1 said:

Basically, you just put more gas after the auto cutoff until you see the gasoline near the brim.

You are fine 99% of the time to top off once, Those cut offs are conservative for a reason. probably best to not make a habit out of it though. Yes, if you continue to top off so much you get fuel to splash back at you, you are going to mess up the evap eventually, go burn the fuel off, EVAP system will rectify itself usually

[Beerzerker]

2 hours ago, Battousai1 said:

Hi guys, I just had a brand new Hyundai vehicle and it is a gasoline one, I had it since 3 days ago.

I made a mistake by not "quickly" reading the owner's manual first specifically the first few pages concerning information about the gasoline to use and break-in instruction.

So from the dealer I went to straight to the gasoline station to put in some fuel and the very first mistake I did was to to "top off" the fuel tank. This is my first brand new gasoline vehicle and all of the vehicles I had are diesel engine vehicles. I just realized after reading and watching videos on Youtube that topping off is dangerous and will damage your "EVAP" system.

The amount of excess fuel I topped off was around 4-5 liters, the fuel tank capacity of my vehicle is 40 liters and I have topped it off at around 45 liters. Although I have not topped it off up to the brim.

After learning that we should not top off our fuel tanks, this will be the first (for gas) and last time that I will top-off the fuel tank.

Now, my question is, is the EVAP system of my brand new vehicle already compromised? Should I bring it to the service center and have the charcoal canister replaced?

The issue you're talking about is when you're stuffing it to the rim, having it overflowing with fuel from the tank fill like some will do.
If you are stuffing it to the gills everytime then yeah, I can see that being a problem to worry about but simply filling it up just once?
Nah.
Your vehicle can handle the tank simply being topped off without hurting anything if you happen to do it - In fact it's designed to handle it as long as it's a regular fillup you're doing.

When the pump handle pops, just stop and you're done... Won't hurt a thing as long as you do it that way. 

And if it happens to really top off anyway for some reason it's not that big or serious of a deal anyway.

[HenrySalayne]

12 minutes ago, Beerzerker said:

When the pump handle pops, just stop and you're done... Won't hurt a thing as long as you do it that way. 

And if it happens to really top off anyway for some reason it's not that big or serious of a deal anyway.

And it won't hurt to fill up to the next "even" amount after the pump stops if you're paying cash or have OCD. With current pricing (in Europe) that's probably not even half a litre. The system has some margin for error.

[Lurking]

EVAP charcoal canister could be soaked with gasoline now. But you also have the problem of expanding gasoline. the gas comes at ground temperature and typically is colder than ambient. then in your car it heats up and expands over time. Warming up of the gas in the car may take some hours.

 

Best course of action is to drive a bit to use up some of the gasoline. Maybe siphon some out if possible? Siphoning may not work on modern cars, though. 

 

I'm sure it happens sometimes and we don't hear about problems. Just don't do it again.

[Needfuldoer]

Yeah, "topping off" is completely unnecessary. 

 

Don't worry about it, but don't do it again either.

[Erioch]

I don't do it.  Is it really worth the extra ounce of gas?  I don't really understand the mentality and I've been fueling cars for over 40 years.

[Lurking]

38 minutes ago, Erioch said:

I don't do it.  Is it really worth the extra ounce of gas?  I don't really understand the mentality and I've been fueling cars for over 40 years.

You still pay for that added gas anyway.

 

In my young years we drove to a close by neighboring country for much cheaper fuel. There we filled it to the brim But that was before EVAP and we would drive 50+ km shortly after filling up 

[Erioch]

3 minutes ago, Lurking said:

You still pay for that added gas anyway.

 

In my young years we drove to a close by neighboring country for much cheaper fuel. There we filled it to the brim But that was before EVAP and we would drive 50+ km shortly after filling up 

I never said it was free gas.  On much older cars it probably doesn't matter but newer cars it could cause damage:

"If you overfill your tank, it can cover the vapor intake hole with liquid gas, which can then be sucked into the charcoal canister. This can damage the canister and possibly other parts of the system, which will cause the car’s check-engine light to come on and could potentially cost hundreds of dollars to repair."

 

It's your car, do what you want.

[Battousai1]

Thanks guys for the replies. What I am worried more is if this one-time topping off has affected the integrity and the accuracy of fuel economy calculations and if the charcoal canister got soaked up already with gasoline, I am pretty OCD specially about the charcoal getting permanently soaked with liquid gasoline. Should I be worried about the charcoal canister and have this checked or replaced or just leave it? The vehicle is brand new and just 3 days old.

Also, based on that Youtube video from speedkar99 there is a float valve mechanism in the fuel tank where it prevents the flow of liquid gasoline to the charcoal canister, is that true for Hyundai vehicles?

[airborne spoon]

there is nothing wrong with topping off after the pump auto cutoff does its thing. Technically you can fill all the way up to the brim of the fuel hole. however, dont do that because gas is a liquid and it expands and if there is no room for it to expand to then that pressures gotta go somewhere and it can lead to cracks or breaks.

 

But usually I'll put about a gallon or so (4-6 liters) in after the auto kickoff engages its perfectly fine as there is still plenty of room for expansion and the vehicle isnt going straight from the gas station to a parking lot and a few gallons are burnt off before the car is ever parked which makes it even less of a deal. But the amount i top off wouldn't hurt even if i did park it all day immediately after filling it up.

[Erioch]

9 minutes ago, airborne spoon said:

I'll put about a gallon or so (4-6 liters) in after the auto kickoff engages

This sounds like a horrible idea for the reason I listed above.

[OhYou_]

51 minutes ago, Battousai1 said:

Thanks guys for the replies. What I am worried more is if this one-time topping off has affected the integrity and the accuracy of fuel economy calculations and if the charcoal canister got soaked up already with gasoline, I am pretty OCD specially about the charcoal getting permanently soaked with liquid gasoline. Should I be worried about the charcoal canister and have this checked or replaced or just leave it? The vehicle is brand new and just 3 days old.

Also, based on that Youtube video from speedkar99 there is a float valve mechanism in the fuel tank where it prevents the flow of liquid gasoline to the charcoal canister, is that true for Hyundai vehicles?

The entire function of the active charcoal canister filter is to convert the fuel vapor created by the tank venting back into liquid fuel and dump it back into the tank. 
it's almost a closed loop system.
it will not matter if you fill it with fuel, just that it will not function as intended and you may start to smell fuel vapors, but it will naturally evaporate the fuel and return to normal function once the fuel level goes lower. 
And that is also assuming the purge valve does not seal. 
 

For a new vehicle, the purge valve should function normally and prevent fuel from backfowing into the evap. 
Now if you actually filled it straight up to the very top, you will instead fill the vent tube which also has a mechanical valve on it to prevent backflow of fuel. This valve should also function as intended and prevent any fuel from passing, but they usually wear out sooner than the pruge valve. 

 

[HenrySalayne]

2 hours ago, Battousai1 said:

Also, based on that Youtube video from speedkar99 there is a float valve mechanism in the fuel tank where it prevents the flow of liquid gasoline to the charcoal canister, is that true for Hyundai vehicles?

That is one of many safety features all cars should have. Imagine if you break sharply with your car and the fuel is flushing around. That would have the very same effect as overfilling the tank.

Don't worry about it, don't stretch it. It's a total non-issue. Fill the tank until the pump stops, add a little bit more if you wish, but don't overdo it. If you overdo it once in a while it's still not the end of the world.

 

I can honestly say I never heard from someone who had damaged their EVAP system with "too much fuel". You just find a lot of people who try to spread awareness for this issue and not a single victim.

[OhYou_]

57 minutes ago, HenrySalayne said:

That is one of many safety features all cars should have. Imagine if you break sharply with your car and the fuel is flushing around. That would have the very same effect as overfilling the tank.

Don't worry about it, don't stretch it. It's a total non-issue. Fill the tank until the pump stops, add a little bit more if you wish, but don't overdo it. If you overdo it once in a while it's still not the end of the world.

 

I can honestly say I never heard from someone who had damaged their EVAP system with "too much fuel". You just find a lot of people who try to spread awareness for this issue and not a single victim.

unfortunately due to the way humans work, this is the case for a lot of information. 
tell someone that if they overfill their tank, it could leak out and ignite, thus killing them? "ehh it wont happen to me"
tell someone that if they overfill their tank it could break some vaguely believable part in their car and cost hundreds of dollars to repair? "oh no i guess i better not do that"

[airborne spoon]

4 hours ago, Erioch said:

I never said it was free gas.  On much older cars it probably doesn't matter but newer cars it could cause damage:

"If you overfill your tank, it can cover the vapor intake hole with liquid gas, which can then be sucked into the charcoal canister. This can damage the canister and possibly other parts of the system, which will cause the car’s check-engine light to come on and could potentially cost hundreds of dollars to repair."

 

It's your car, do what you want.

I've been filling cars and trucks like this for over 30 years and aint shit broke yet so I'm inclined to believe its a non-issue.

 

[Erioch]

I mean, the even owner's manual says not to do it so it must've caused problems at some point.  But, like I said, it's your car do what you want with it.

 

In my 40+ years of fueling cars, I've seen people smoking at the gas pumps and, I assume, nothing has happened to them ... so far.

[Beerzerker]

1 hour ago, OhYou_ said:

unfortunately due to the way humans work, this is the case for a lot of misinformation. 
tell someone that if they overfill their tank, it could leak out and ignite, thus killing them? "ehh it wont happen to me"
tell someone that if they overfill their tank it could break some vaguely believable part in their car and cost hundreds of dollars to repair? "oh no i guess i better not do that"

Had to fix that.

Using YouTube as a basis for everything isn't the best idea, I mean there are plenty of informative vids out there with some good content too but you also have misinformation out there.

I can spot misinformation about this kind of subject considering what I used to do for a living. Whatever vid was saying it's a disaster in the making was spewing such.
I know not everyone has the knowledge/experience myself or others have, that's true but when you think about it the engineers that designed the fuel evap system already knew some raw fuel would get in on occasion because of a possible overfill or as another said about fuel sloshing around.
With that in mind I'm sure they took that into account when it was designed so it woudn't cause a problem if it happens every now and then.

[RasmusDC]

i don´t know how they operate in the place your from, but Kia and Hyundai here fix everything on warrenty without being a hassle.

 

I am sure that if by some "unlucky" element, you end up having an issue, then just warrenty it, it is not a thing that destroys expensive parts on the tank.

 

i know people that overfill daily on cars, and i don´t know they have ever had an issue with it. i don´t know why you have to brim it. but of course the cars needs an ability to "burp"

 

So i guess it is a MUCH bigger issue, if you end up filling the car up, not driving it, and just letting it stand, because then you can have hot / cold expansion, that can give you issues.

[Bombastinator]

On 3/28/2023 at 6:55 AM, Battousai1 said:

Hi guys, I just had a brand new Hyundai vehicle and it is a gasoline one, I had it since 3 days ago.

I made a mistake by not "quickly" reading the owner's manual first specifically the first few pages concerning information about the gasoline to use and break-in instruction.

So from the dealer I went to straight to the gasoline station to put in some fuel and the very first mistake I did was to to "top off" the fuel tank. This is my first brand new gasoline vehicle and all of the vehicles I had are diesel engine vehicles. I just realized after reading and watching videos on Youtube that topping off is dangerous and will damage your "EVAP" system.

The amount of excess fuel I topped off was around 4-5 liters, the fuel tank capacity of my vehicle is 40 liters and I have topped it off at around 45 liters. Although I have not topped it off up to the brim.

After learning that we should not top off our fuel tanks, this will be the first (for gas) and last time that I will top-off the fuel tank.

Now, my question is, is the EVAP system of my brand new vehicle already compromised? Should I bring it to the service center and have the charcoal canister replaced?

As long as what you put in wasnt diesel it’s fine.  It is dangerous.  So dangerous that it isn’t allowed to happen.  If you overfill your tank the excess gasoline will just be vented off.  So you hurt the environment.   It’s possible I suppose that newer vehicles lack this vent.  The old ones all had it though.  Safety feature.  If it turns out you DON’T have one in that vehicle you could always siphon out the gas.  Back in the 70’s people would steal gas that way.  People bought locking gas caps. All you need is a hose and strong lungs, or a hose and a little hand pump.  A piece of garden hose was popular.

Edited March 29, 2023 by Bombastinator

[Lurking]

Just make sure you act like you know of nothing if you need to have it repaired under warranty

 

With Hyundai/Kia the lack of engine immobilizer is a larger worry anyway.... in our area there are dozens of Hyundai/Kia thefts because thieves figured out they skimped on the engine immobilizer. Here the Police hand out free steering wheel locks for H/K owners to prevent thefts. And insurances refuse to cover H/K. So that little over-filling wouldn't be my biggest worry... 

[Needfuldoer]

On 3/28/2023 at 1:06 PM, Battousai1 said:

What I am worried more is if this one-time topping off has affected the integrity and the accuracy of fuel economy calculations

Nah. 

 

Miles driven divided by gallons filled. There's your fuel economy calculation.

 

On 3/28/2023 at 1:06 PM, Battousai1 said:

I am pretty OCD specially about the charcoal getting permanently soaked with liquid gasoline.

Gasoline evaporates.