Just an FYI - You should never "top off" the fuel tank.

[karinbelle]

I reposted this in its own thread because I thought it might help a few more people.

Just an FYI - You should never "top off" the fuel tank.

Here's why.

The "extra" fuel you think you are getting into your tank actually goes back into the gas pump to avoid spilling the gas and contaminating the air.

This is a safety feature to prevent gasoline spills, which can harm ground level air quality.

So that "extra" fuel you think you are putting in the tank (or the nice round number you are putting on your credit card) is just a bonus payment to the gas station.

This I learned from an air-quality educator in a large municipal city.

hipchickie confirmed the information independently in the other thread started by TaraPA.

Original thread here: http://www.disboards.com/showthread.php?t=2723258

 

[NYCDiane]

I always pump my own gas because, no matter how many times you tell the guy DO NOT TOP IT OFF, they will always try to bring it up to the next dollar even if you stopped at a 27 cent mark. Then, they pull the handle out and there's gas spilled all over the side of the car and on the ground,

This has happened too many times so now I just go to self serve and stop when it clicks.

 

[Purseval]

I find that incredibly hard to believe, not for the fact that there is a safety feature but that there wouldn't be some consumer advocacy group screaming bloody murder about the evil oil companies ripping off consumers out of hundreds of millions of dollars in "topoff overcharges" every year. Could you post a link to that info please?

 

[GinnyEmma]

http://www.epa.gov/donttopoff/

 

[Fyrefly]

Absolutely true. And if you don't refrain from doing it to save gas money, there is the risk of fuel from an overfilled tank getting into your EVAP system and doing major damage to your vehicle.

Sources as PP requested:

Government site (for all the bad web design I'd say the EPA is credible)
http://www.epa.gov/donttopoff/

Other sources from a fast google:
http://www.sbcapcd.org/edu/dont-top-off.htm
http://ask.cars.com/2007/07/gas-top-off.html

And part of a Toyota Prius handbook which details the system in question which can be damaged (see page 3)
http://www.autoshop101.com/forms/Hybrid13.pdf

 

[MomToOne]

Here's something from the EPA on it:

http://www.epa.gov/donttopoff/

But notice they say the fuel MAY get diverted back to the station tanks. I suspect that happens only once you actually overfill your tank, which of course would never want to do. I don't know that topping off a few cents worth would end up diverted back, if it still fit into your tank.

 

[karinbelle]

Here's something from the EPA on it:

http://www.epa.gov/donttopoff/

But notice they say the fuel MAY get diverted back to the station tanks. I suspect that happens only once you actually overfill your tank, which of course would never want to do. I don't know that topping off a few cents worth would end up diverted back, if it still fit into your tank.

Thank you GinnyEmma, Fyrefly, and MomtoOne. I knew there would be skeptics.

 

[Disney845]

I always pump my own gas because, no matter how many times you tell the guy DO NOT TOP IT OFF, they will always try to bring it up to the next dollar even if you stopped at a 27 cent mark. Then, they pull the handle out and there's gas spilled all over the side of the car and on the ground,

This has happened too many times so now I just go to self serve and stop when it clicks.

I just wanted to say that I smiled when I read about this. I have never lived anywhere with a full service gas station, it is always self pump. When I was younger and had heard about it (or saw attendants pump in older movies/TV) I just thought it was something that had stopped with the ages. Then, about 8 years ago, I was driving from IN to FL and stopped at an exit that actually had an attendant pump gas option (they had self serve too). I was so excited to see this, as I didn't really think they still existed (small things clearly amuse me ).

I actually wish we had full service here. I HATE pumping my own gas. I generally wait until SO and I are out together (we usually drive my car, not his, if we are going anywhere together because mine is more comfy for a passenger -roomy sedan vs a small 2 door sports car) so that he can see I am low on gas and pump it for me. In fact, just the other day I told him he needed to take my car to work that day and I would drive his because I was on empty and wanted him to pump the gas for me!

 

[GinnyEmma]

Ftr, I always check for snopes on stuff like this. It sounds like an email thing.

 

[sam_gordon]

From a practical standpoint (I have no links or studies, just what I've noticed with my own eyes)...

When I'm filling my lawn mower gas can, as the gas goes in (at a decent pressure), it "foams" at the top, creating a "false full" reading. Remember, I can SEE the level of the gas. So the pump kicks off, I count to 3 maybe, and the foam has dissipated and I can put more in.

I can do the same thing use the spray attachment on my sink or hose. Turn the water on full, then use the sprayer in a bucket or water jug or something. Watch the top... it will bubble and foam. Stop spraying and you've "lost" water.

 

[bumbershoot]

I actually wish we had full service here. I HATE pumping my own gas.

Move to New Jersey or Oregon, and you'll have it all the time. It's mandated that you cannot pump your own gas in those states...if you get out of your car they'll get all nervous and yelp at you! I believe it's a job-creating thing in those states.

 

[KELLY]

My van won't top off. When it stops it is done. If you do it will over spill has happend to me 2 times. After the second time I learned my lesson.

 

[MrsPete]

Let's think logically:

If the gas is going back into the tank, then you'd NEVER reach a point that no more could go into the tank. You could rack up a bill in the hundreds and you could still keep "topping off".

Topping off does eliminate the air in your tank, and that means your gas can't expand and will possibly overflow your tank. So topping off is a bad idea, but not for the reason explained.

 

[Purseval]

Thank you GinnyEmma, Fyrefly, and MomtoOne. I knew there would be skeptics.

There still are. As others have noted, anyone who has ever owned a lawn mower deals with the auto shutoff all the time and, because it's something they can see as opposed to a hidden car tank and gas line, they know when the can is full and the price matches the amount in the can. Also noted was that vapor recovery systems kick in when the tank is overfilled to the point of spilling over, not when you are trying to round off a $39.62 purchase up to $40.00. Interesting links, tho. Thanks for posting them.

 

[luckyfin]

Move to New Jersey or Oregon, and you'll have it all the time. It's mandated that you cannot pump your own gas in those states...if you get out of your car they'll get all nervous and yelp at you! I believe it's a job-creating thing in those states.

This is so true! They really do freak out a little if you get out of your car

 

[Promomx2]

My dh used to do this to the point he would shake the car to get "every drop" in the tank. The kids and I made such a stink about it he finally stopped.

 

[LisaNJ25]

This is so true! They really do freak out a little if you get out of your car

yep... since it agaist the law. I love not having to pump my own gas.

 

[karinbelle]

Ftr, I always check for snopes on stuff like this. It sounds like an email thing.

Does snopes dispute it?

This was not an e-mail thing, just information from my personal experience with an expert in air-quality. Please check out the numerous sources above.

 

[Purseval]

This was not an e-mail thing, just information from my personal experience with an expert in air-quality. Please check out the numerous sources above.

Your information was correct, you just overstated the impact it has. In your OP the statement: So that "extra" fuel you think you are putting in the tank (or the nice round number you are putting on your credit card) is just a bonus payment to the gas station. gives the impression that some significant quantity of fuel is lost, which lead to questions as to why no consumer group has questioned it, why you can't pump back some infinite quantity of fuel and not notice it, etc. I believe the reality is more along these lines:

1. You start off with a hose full of gas that was actually pumped by the previous customer. This is done to ensure no delay in pumping and, since everyone gets that same hoseful of gas, it's a wash.

2. You start filling the tank until it shuts off automatically, indicating a full tank. You ignore it and go to top it off.

3. The gas keeps flowing as you defeat the auto shutoff until it reaches a point where the gas has nowhere to go but backwards. It fills the nozzle, pushing a bit back down the hose with the force, then the gas forces itself past the sides of the nozzle and down the side of your car, soaking your feet in gas as you finally decide to let go of the handle.

The actual gas flowing backwards into the tank is minimal, which is why no consumer groups are screaming over the evil oil companies ripping off the consumers. That, plus the fact that nobody wants to defend someone with stinky gas feet

More of an impact is something others have stated, the chance to ruin a few sensors. If you've ever had a check engine light come on after a fillup that's usually what is causing it.

 

[LovableGluttons]

My dh used to do this to the point he would shake the car to get "every drop" in the tank. The kids and I made such a stink about it he finally stopped.

LOL You made me laugh out loud!

I'm just picturing a guying shaking his car with his wife and kids inside. LOLOL