Do not overfill or top off while filling gas tank

[Steve Wolf]

I learned a lot when I topped off a 100+ gallon tank on a motorhome I had. The temperature went from about forty degrees to eighty plus that day. "Oh, the gasoline expanded. My motorhome is peeing gasoline. But it will stop soon."

No, it won't.

No, it didn't.

I poked that bear once and got away with it. You all go ahead and poke your own bear. I'll watch.

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[Tim d]

They have similar warnings for the hybrid but below is the warnings from Ford on owners manual non hybrid.

https://www.fordservicecontent.com/...A&div=f&vFilteringEnabled=False&buildtype=web

FYI the way I read this is the damage and possible fire or explosion from it. Just wondered in 50 years you picked up a gas can and went to open it and it spurted fuel because the gas in the can expanded and pressurized. I'm wondering if this is what or why the warnings. Fumes are explosive, where gas is combustible. Then again what do I know, besides the warnings Ford put in the owners manual.

Plenty of warning but specifically look for this one on refueling

▲ WARNING: Stop refueling when the fuel pump nozzle automatically shuts off for the first time. Failure to follow this will fill the expansion space in the fuel tank and could lead to fuel overflowing.

Good point, and yes that has happened, but i don't smoke, and no smoking at gas stations, even though I know there are some idiots out there!

 

[Hunters Edge]

Good point, and yes that has happened, but i don't smoke, and no smoking at gas stations, even though I know there are some idiots out there!

That maybe, have you ever wondered why your gas mileage may be different from one time to the next? You could have lost gas without even realizing it going down the road. They are not just referring to expansion while filling. Of course I could be wrong but it seems the expansion chamber is there to allow the fuel to expand without dumping or spewing it on the ground.. if you are going down the road you maybe oblivious of what's happening. It pretty well is open to interpretation but calling it an expansion chamber clearly in my view is designed to handle the expansion of gas expanding, not filling it up with gas JMHO

 

[TwoTone]

I love all the I've been doing it for X years. It's amazing how cars haven't changed over time.

 

[tciotti2003]

This happened to my wife's 2011 Kia Optima. I was the one who would top off the gas tank. I used to do this all the time on my 04 Toyota Matrix never having an issue but it seems with the newer cars the purge valve can get messed up

 

[sapperforward]

This has been posted before I'm sure. Just doesn't hurt to remind everyone and to offer the information to new members.

https://www.dailydot.com/news/overfilling-gas-tank-warning/?amp

I don't top off per se but I do round it to the next dollar I don't like leaving change on my CC

 

[HeyBales]

That maybe, have you ever wondered why your gas mileage may be different from one time to the next? You could have lost gas without even realizing it going down the road. They are not just referring to expansion while filling. Of course I could be wrong but it seems the expansion chamber is there to allow the fuel to expand without dumping or spewing it on the ground.. if you are going down the road you maybe oblivious of what's happening. It pretty well is open to interpretation but calling it an expansion chamber clearly in my view is designed to handle the expansion of gas expanding, not filling it up with gas JMHO

There is a more serious filler top lock than the external panel.
Gas isn't sloshing out on the road.

You also need to realize most of the people you are talking to have said not topping off like the article is talking about, from their own descriptions.
They aren't waiting until they see gas at the top. Which could only happen if you have a bad pump handle.

Doing a few clicks to make up for variability of shut-off mech's is very different than 20 clicks that eventually by-passes that safety mech.

As to the fact there is a warning in the manual about it - there are all kinds of warnings in there that sane people don't really need, but they have to be included now because of idiots.

From the section on fueling.

• Automotive fuels can be harmful or fatal if swallowed. Fuel is highly toxic and if swallowed can cause death or permanent injury. If fuel is swallowed immediately call a physician, even if no symptoms are immediately apparent. The toxic effects of fuel may not be apparent for hours.

 

[Hunters Edge]

I don't top off per se but I do round it to the next dollar I don't like leaving change on my CC

Wow that's pretty good. I have a fricken hard time even trying to stop it on a certain amount. Watch a show, maybe (60 minutes) years ago maybe decades about filling gas at a lower speed gets more gas and less air. Anyway I usually just put it at low and clean my windows. Hate bird crap, bugs, salt, mud etc on the windows.

So your telling me when you pay your charge card off each month you have no change from restaurants, grocery store etc . I think it maybe a little OCD going on there. I fill a lot of gas and diesel fuel cans for the farm. I just try not to overfill the line on the cans otherwise makes it difficult not to spill any when trying to fill tractors, rototiller, lawnmower, chainsaws etc. In other words I don't even try to round off the numbers anymore. Those fuel cans kind of curbed me from what your experiencing.

 

[Hunters Edge]

There is a more serious filler top lock than the external panel.
Gas isn't sloshing out on the road.

You also need to realize most of the people you are talking to have said not topping off like the article is talking about, from their own descriptions.
They aren't waiting until they see gas at the top. Which could only happen if you have a bad pump handle.

Doing a few clicks to make up for variability of shut-off mech's is very different than 20 clicks that eventually by-passes that safety mech.

As to the fact there is a warning in the manual about it - there are all kinds of warnings in there that sane people don't really need, but they have to be included now because of idiots.

From the section on fueling.

• Automotive fuels can be harmful or fatal if swallowed. Fuel is highly toxic and if swallowed can cause death or permanent injury. If fuel is swallowed immediately call a physician, even if no symptoms are immediately apparent. The toxic effects of fuel may not be apparent for hours.

You might want to research that info.

Yes, if you overfill a car's gas tank, the excess fuel will simply spill out, effectively relieving pressure by physically overflowing past the tank's capacity, essentially "weeping" out as the tank can't hold any more fuel; this is why most gas pumps have an automatic shut-off mechanism to prevent overfilling.

Key points about overfilling a gas tank:

No significant pressure build-up: Unlike a sealed container, a car's gas tank isn't designed to hold high pressure, so overfilling primarily leads to liquid fuel spilling out.

Potential damage to the system: While the immediate effect is just spilling gas, consistently overfilling can damage the car's evaporative emission control system, leading to potential check engine light issues.

Environmental concerns: Spilled gasoline can contaminate the ground and contribute to pollution.

 

[HeyBales]

You might want to research that info

Yes, if you overfill a car's gas tank, the excess fuel can simply "weep out" due to the tank reaching its capacity, effectively relieving pressure by spilling onto the ground; most modern cars have a fuel pump shutoff mechanism to prevent major overfilling, but it's still important not to "top off" your tank past the first click to avoid potential issues with the evaporative emission system.

If the 1st click was accurate and not a bad mech - then the 2nd click is going to add mere ounces of fuel.
(if 1st wasn't accurate due to fast flow sloshing - then 2nd click after a pause of 30 seconds and using slow flow rate may had more than a bit, proving out the 1st was early)

If you think a few ounces is the difference between happy EVAP system and expansion tank working as designed - or explosions and weeping due to filling up expansion tank and killing charcoal canister and purge valve - your vehicle has serious design flaws.

How would the modern car's fuel pump prevent major overfilling?
If you got that idea from TikTok - don't listen to that person anymore.

 

[MakinDoForNow]

That maybe, have you ever wondered why your gas mileage may be different from one time to the next? You could have lost gas without even realizing it going down the road. They are not just referring to expansion while filling. Of course I could be wrong but it seems the expansion chamber is there to allow the fuel to expand without dumping or spewing it on the ground.. if you are going down the road you maybe oblivious of what's happening. It pretty well is open to interpretation but calling it an expansion chamber clearly in my view is designed to handle the expansion of gas expanding, not filling it up with gas JMHO

At least in hybrid the tank is pressurized to help reduce venting of lighter more easily evaporating ozone depleting components in gasoline. There needs to have room for them to evaporate into as well as for the pressure to keep rate of evaporation down.

 

[boxster03]

I top off until at least a gallon overflows onto the ground

 

[Glen Baker LLC]

I top off until at least a gallon overflows onto the ground

Nothing as satisfying as topping off the tank. Getting those extra 4 miles in
That's how we roll.

 

[Shelbyv8]

You can do what you want, your choice. Don't come on here and tell me I am stupid for doing an additional TWO clicks. I have done it for at least 50 years on at least 50 vehicles with zero problems.

 

[tom_tucker]

I'm good with the first click and 500 mi on the tank, don't need 600. The only time I say "top off" is at the go-go club. It's a better way to get a nice lap dance.

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