is "topping off" after fill up harmful?

[eljefino]

My prius has an internal tank bladder that gets stiff when cold so I fill to the click and let it sit for a few seconds so the bladder can unfold itself. Then I trinkle a little more in. The "unleaded restrictor flap" is long gone so I can pull the nozzle out a bit and watch it go down.

I find BJ's wholesale pumps the most aggressive in forcing gas in, sometimes to the point of hilarious eruptions.

My 02 camry did not like being topped off. I either mucked up the EVAP hoses or the Spectra brand replacement tank lacked a baffle, but it would slug raw gas through the EVAP system into the intake if chock full of fuel.

 

[Propflux01]

Has not bothered either Elantra for the 5 years I've had them.I usually get about a gallon more in it after the click-off.

 

[joekingcorvette]

There is no way possible to top off my 2005 Corvette. When the hose clicks off it's 100% full and even a little squeeze of the gas nozzle will cause it to backflush. I top off my 2012 Honda Civic all the time. When I went to Oregon they pump the gas for you unless you have a sport car like a Corvette. They let me pump my own gas. I have never had a problem with filling any vehicle up all the way past the first click.

 

[Wolf359]

Originally Posted by mclasser
I don't top off. I cringe when I see other people do it. Whenever driving thru NJ, I avoid stopping for gas there. If I have to, I tell the attendant not to top off.


Then where do you go? I normally love stopping in NJ for gas when passing through, I usually fill up with just enough gas to make it to the NJ border and then fill up when I'm there. Then I fill up again just before leaving. it's good for breaks anyway. They usually have the lowest price of the surrounding states.

 

[Leo99]

My wife always went to cheapo gas stations in NJ where they would top off the tank. After 320k miles, it took 2 tries to start the car after she bought gasoline. I replaced the canister for $250 and the problem went away.

My conclusion is that topping off is bad but it is going to take a few miles until you see any issues. Although, after 320k miles, who knows if topping off was the real root cause.

I don't think it's that big of a deal.

 

[Revving2Redline]

Top off to next .25 but never filled it to the point I was having it flow back at me.

 

[edwardh1]

Originally Posted by rooflessVW
It can kill your carbon canister and force liquid fuel where it doesn't belong.


This

 

[fdcg27]

Originally Posted by Brybo86
i routinely add an extra 2-3.5 gallons to my 2008 Honda Accord after the pumps auto shutoff (usually only do this if i have the time ((because you have to hold the trigger at about 1/4 flow)) and or we are on a road trip and trying to stretch a few more miles between stopping and waking up the kids) (don't do this if the temp is -22F outside like this week)

been doing this for 6 years..... and 150k miles
never a CEL...
i can go about 160 miles before the fuel gauge needle even moves....

my 1995 Lexus LS400 will only take about 0.5 gallons extra after the pump auto shutoff

i think all the signs on pumps are because they don't want people spilling a drop of gas and its god awful effects on the environment
i don't spill because well that would be wasting money.


^^This!!
We also have a Gen 8 Accord and the tank actually holds quite a bit more than the rated 18.5 gallon capacity.
I always really filled the car to the brim when it was in my hands with no problems whatever in the 96K it lived with us. It's now in the hands of a son who will probably never really fill it. It would indeed take some miles before the needle moved off of full.
This Accord would always give more than 500 miles on a tank and 600 would have been possible under favorable conditions although around 590 miles was as far as I dared go under the baleful glow of the low fuel indicator, even though the OM said that this came on with 2.8 gallons remaining.
I've been giving our cars true fills for decades now with never an issue of any sort with any of them, so I'm not so sure that flooding the charcoal canister with liquid fuel ever really happens.
After all, the system can't be that simply engineered that it fails to allow for real tank fills.

 

[tiger862]

My Caravan will stall if overfilled. It did it only once that I decided to fill up to next dollar amount never did it again as I now stop at first click unless it is close to next nickel and it is always passed full. When talking to tech I was told a protection of carbon filter vent sent raw unregulated fuel to engine causing a flood condition which caused a stall. Who knows why the stall on top offs but it happened to me.

 

[StevieC]

I've have not had an issues in the current Caravan and previous vehicles (sometimes full-serve will do it), but I can see how it can be a problem depending on the vehicle. That said I just stop when the pump does. I'm forever at a gas station refilling with the miles I drive so it doesn't matter to me if I try to squeeze another bit in there.

 

[Skippy722]

Originally Posted by tiger862
My Caravan will stall if overfilled. It did it only once that I decided to fill up to next dollar amount never did it again as I now stop at first click unless it is close to next nickel and it is always passed full. When talking to tech I was told a protection of carbon filter vent sent raw unregulated fuel to engine causing a flood condition which caused a stall. Who knows why the stall on top offs but it happened to me.


The 2018 GC in your signature? My parents 2004 started doing that when it was about 4 years old... mechanic told us there was a valve broken allowing raw fuel to get into the canister, and when the computer sends a purge command it dumps that raw fuel in causing it to stall. But, it never set a check engine light and runs great the rest of the time so they never bothered fixing it. At least that's how my barely teenage mind understood it at the time lol

 

[demarpaint]

Occasionally my Liberty will spit gas back. I fill until it stops, and round to the nearest nickle. I keep change in the Liberty for that reason. Even after having the gas tank replaced twice under the lifetime campaign for the issue, the problem is still present at times.

 

[DGXR]

Let's just say there's a reason why the pump clicks off when it does. Fuel tanks are designed to have a certain amount of headspace, and if that is filled up, you *could* have a number of problems... all of your own making. The extra ounces (or even an extra gallon) are definitely not worth the potential trouble.
If it really makes that much difference to you, it's possible that you have other problems not related to the vehicle.

 

[HighbrowHillbill]

Originally Posted by 69GTX
Before the days of carbon canisters and numerous credit cards many more of us topped off to the nearest dollar or 50c.

Always have, most likely always will.