wb6yyz
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Wilkes Barre/Scranton Area
Posts: 5,557
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Post by wb6yyz on Oct 23, 2018 13:43:37 GMT -5
The question of the week is: Do you "top off" your gas tank after the pump shuts off?
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wb6yyz
Champion Member
Wilkes Barre/Scranton Area
Posts: 5,557
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Post by wb6yyz on Oct 23, 2018 13:47:14 GMT -5
And my comment and vote is NO! On a modern gasoline powered car, topping off the gas tank has a good chance of damaging the emission control components. Specifically, overfilling the gas tank can cause liquid gas to enter the charcoal canister, or carbon filter, which is designed only for vapor. If you live in one of the areas (most major metro areas) that have the goofy gas pump nozzles, you might actually pump gas back down that vapor recovery system and into the gas station storage tank and not even get the gasoline you are paying for!
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Deleted
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Post by Deleted on Oct 24, 2018 2:20:03 GMT -5
And my comment and vote is NO! On a modern gasoline powered car, topping off the gas tank has a good chance of damaging the emission control components. Specifically, overfilling the gas tank can cause liquid gas to enter the charcoal canister, or carbon filter, which is designed only for vapor. If you live in one of the areas (most major metro areas) that have the goofy gas pump nozzles, you might actually pump gas back down that vapor recovery system and into the gas station storage tank and not even get the gasoline you are paying for!
first we have to start at the "car" the end of the line for the fuel used.
the car is the only place that the fuel lives that is not a "passive" environment. modern gas tanks have "humps" molded into the top of the fuel tank. these humps hold between a few gallons and up to around five gallons of fuel . these humps are above where the fuel filler enters the tank , these cannot be filled by the "pumper" they remain empty and are for expansion of the fuel like on a hot day with a tank of cold fuel. above these humps are where the vapor recovery hoses connect , the fittins on these hoses contain little balls the rise to the top when liquid hits them, to close off the lines themselves, this is both to protect the emissions system in case you park on a steep incline with a full tank and also to protect from a fuel spill in case of a roll over. the only way to fill the tank enough to cause damage would be to tip the car on it's side(filler faceing up) and then fill the tank. and then the check balls would then shut down the vapor recovery system. you might damage the vacuum pump used to check your vapor recovery system and then only if your car was doing for a "vapor recovery test" before you had a chance to use up a gallon of fuel.
As far as the fuel filling up the gas line on the gas pump at the station. it just can't be done. the station uses a passive recovery system. there is no pump just the normal vapor leaving the filling tank that goes back to the emptying tank at the station your pulling gas from. it is a closed loop. if somehow you got a 100% seal between your filler neck and the pump nozzle and if you also had a nozzle that did not prevent fuel from shutting it off (hard to do because modern nozzles are really sensitive to fuel backing up in the nozzle) you might have a little fuel in the vapor hose ....if you did it would spill all over the ground when you removed the nozzle, there's simply no suction to pull anything back to the gas stations tank.
I think a lot of these "rumors" or "wives tails" tarted back in the 70's . cars back then did not have all the protections they have today and you did have vapor canisters filling with gasoline and ruining parts of emissions systems but from around the early 90's you simply can't screw it up.
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wb6yyz
Champion Member
Wilkes Barre/Scranton Area
Posts: 5,557
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Post by wb6yyz on Oct 24, 2018 13:35:27 GMT -5
I am thinking of the older model cars and the early vapor recovery systems at the gas stations. Where I live now it's too rural for a gas station vapor recovery system. I think it's been two years since I last was at one, either my last trip to California or maybe when I had to stop for gas in Philly once. Stands to reason that the car vapor recovery systems would have been redesigned to keep them from getting messed up by "topping off". Still don't want to risk spilling gas. Too expensive these days to waste even a drop!
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Post by Interesting on Oct 27, 2018 1:43:33 GMT -5
What about if you're pretty sure the pump nozzle shuts off well before the tank is really full... Then again I'm pretty bad about this, I tend to fill to the next 25ยข mark for no good reason.
Then there is another GB poll I think a long time ago... do you try to extract the last drop from the nozzle? Y/N
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mnrick
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Post by mnrick on Nov 11, 2018 16:36:35 GMT -5
No, once it stops automatically I am done.
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Post by g67tdi on Dec 1, 2018 20:33:39 GMT -5
I top it off because the automatic shut off goes off way before my tank is full on my Subie Outback. I can put another $5 in it easily if I let it fill slowly instead of full speed. When it shuts off automatically after filling more slowly, I stop. Doesn't make sense to leave more than a gallon of empty tank. This means less range and more frequent fillups. On my F-150, it is different. When the pump clicks off, it is full. If I try to put more, it often spills out. I guess these differences have to do with the curves and diameter of the filler hose.
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Deleted
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Post by Deleted on Jan 24, 2019 14:14:43 GMT -5
I sure do...Just today the pump stopped at $11.01, slowly but surely I pushed it all the way to the $12.00 dollar mark.
I rather be fully FULL, than EMPTY, with either a bad Gas Pump or walking a few miles to get one gallon of gas for being negligent/ aka CHEAP !!!
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Deleted
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Post by Deleted on Feb 1, 2019 8:55:37 GMT -5
BUT, I read that yes to running on fumes all the time it's bad for the vehicle, by the same token, topping off AFTER the pumps stop is also not a good thing to do either, therefore I will stop that habit from now on.
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Deleted
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Post by Deleted on Mar 18, 2019 14:21:35 GMT -5
For years now, my debit card with BoA (Bk of America) has a feature that anything under a dollar gets rounded up to the next dollar, and the difference gets transferred to a savings acct with them..The 1st yr in the Program they matched every contribution 100%, after that it's all you money, but it's amazing how much money is transferred to the savings every month..
So if the Pump stops now at 5 cents over the dollar, I stop and .95 cents get transferred to savings within 24 hrs.
Just another good way to save cents that ultimately add a decent ammount when you look at it yearly.
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Post by MadFueler on Mar 31, 2019 20:26:00 GMT -5
Yes - always.
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Deleted
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Post by Deleted on May 23, 2019 13:30:01 GMT -5
I did today,but never to the POINT of having Gas Come up and back out the Tank !! No Way !
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Post by SUVFan on Jul 26, 2020 15:38:21 GMT -5
I used to when I paid cash in the olden days. I've been paying with plastic for years and no longer bother. If the auto shutoff goes off when I know the tank's not nearly full (rarely), I don't consider restarting the pump to be topping off. That's still filling the tank to a normal point.
Every once in a while, when I'm trying to use a dollar off in Kroger's program and if I have not pumped 35 gallons into my gas tank and my Jerry cans are full (that means I probably underestimated and didn't bring enough cans!), I'll squeeze a little more into the gas tank.
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