# Topping off tank: Worthwhile?



## BradHerr (Sep 29, 2013)

I agree with your theory of a known quantity of fuel and I always fill my CTD up to the neck. I consistently get 17+ gallons in my car and it doesn't hurt anything. It does take some time to fill it that full though, and I noticed some stations have better pumps for topping off than others. Some pumps will allow a very little amount of fuel to trickle out of the nozzle and have a more "variable" delivery control valve and others seem to be an "on-off" style control valve. The later foams up more and is more likely to overflow a little fuel. From experience, the pumps usually auto shut off around ~14 gallons and I can squeeze ~3 more gallons. 

***edit****
One caveat- I have a 90 mile commute and I always fill up BEFORE driving to or from work. I never fill up and let the car sit. There could be some expansion of the fuel if left to sit topped off for a extended period of time. I have not tried to let mine sit to see if it would hurt anything. 

-Brad


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## Jorday (Jul 30, 2013)

Yeah it's worth it to me just because it adds 100+ miles of range. It does take a few extra minutes but after 6 tanks or so you save yourself an entire fuel stop. So in a way you do get reimbursed for some of the time.


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## KpaxFAQ (Sep 1, 2013)

Worth it to some, not to most. Cool that it can be done though!


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## CHEVYCRUZE RS (Mar 29, 2011)

I fill up until the pump auto stops, im sure the tank has had enough


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## TheGov (Feb 12, 2014)

LemonGolf said:


> I posted the below in the economy section a little while ago, but it hasn't received any feedback..I pick up my CTD tomorrow (finally!)


 My production date is not until Monday.

Hopefully I will have mine second or third week in May.

Post pictures when you get her.


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## obermd (Mar 3, 2012)

If you're after valid long term MPG (l/100KM) figures you do it the same way regardless of fuel. Record every fill up gallons (liters) and the primary odometer mileage (kilometers). You can track on paper, in a spreadsheet, or on-line at www.Fuelly.com or Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com. Fuelly has Android, IOS, and mobile web interfaces to record your information before you pull away from the pump. By doing it this way it doesn't matter if you fill the tank completely or have an early pump shutoff. You're looking for long term averages.

If you go with fuelly or ecomodder you can add your long term information to your signature block on CruzeTalk.


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## Scott M. (Apr 23, 2013)

My only concern is that I have read that the fuel pumps at the stations aren't as accurate when you start and stop the pumps. So you may not get as much fuel as you think. Likely its not a significant amount though.


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## BradHerr (Sep 29, 2013)

Scott M. said:


> My only concern is that I have read that the fuel pumps at the stations aren't as accurate when you start and stop the pumps. So you may not get as much fuel as you think. Likely its not a significant amount though.


I haven't done any research on the accuracy of the fuel pumps while stopping and starting, but most pumps have a sticker on them that says "accurate at all pressures and deliveries" 


-Brad


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## obermd (Mar 3, 2012)

Most jurisdictions require gas and diesel pumps have their flow accuracy certified annually.


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## Sperry (Aug 3, 2013)

I usually fill normally for the first 45 liters and then stop for about 15 seconds to let some the form settle.. From there I slow the fill down bit until I hear hear it coming up the neck.. Wait another 15 seconds and resume even slower.. First click then round off to next dollar very slow.. You can try to really top off your tank even more if you want.. Over filling will effect your first mpg a bit but it will average out the same over few tanks


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## Barefeet (Jan 1, 2014)

I was filling my tank before a 600 mile trip, I thought if I could fill it to maximum I might not have to refill until I got home. The nozzle clicked off and I gave it another squeeze, it shut right off again. I took a look into the fill pipe, it would have been a nice head if I was pouring beer. I was about to start trickling in a little at a time when a large pickup truck pulled up. The rather large driver was looking at me, I was looking at the foam coming up in the fill tube I took another look at the driver and decided not to test his patience. Maybe another time.


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## plasticplant (Mar 26, 2013)

I like to fill on the slowest pump setting. When it clicks off, I wait 1 minute (usually clean the windows). Then I go back and slow trickle more fuel until the foam almost pours out. I then wait 30 seconds and then fill until it foams again. Then I pull up the Fuelly app and start entering my data. I fill again until the foam comes to the top, log the gallons and call it a day. Seems to give me pretty accurate results. Every fill up I put in between $58-$60.


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## obermd (Mar 3, 2012)

plasticplant said:


> I like to fill on the slowest pump setting. When it clicks off, I wait 1 minute (usually clean the windows). Then I go back and slow trickle more fuel until the foam almost pours out. I then wait 30 seconds and then fill until it foams again. Then I pull up the Fuelly app and start entering my data. I fill again until the foam comes to the top, log the gallons and call it a day. Seems to give me pretty accurate results. Every fill up I put in between $58-$60.


What's your price per gallon? My average fill up price over 47,000 miles is less than $33 and I run premium gas. My average fuel cost per mile is 8.2 cents.


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## plasticplant (Mar 26, 2013)

obermd said:


> What's your price per gallon? My average fill up price over 47,000 miles is less than $33 and I run premium gas. My average fuel cost per mile is 8.2 cents.


In the summer months, I usually run the tank down to just before the fuel light comes on (about 600-660 miles). Since I bought the car in mid Aug, diesel has been anywhere from $3.79 - $3.99. Its been holding strong now at $3.89. Fuelly says I'm at 10.8 cents a mile. I'm very happy with that, as i am not a hypermiler and enjoy using the power this car offers. I think that number will start to drop now, as most of my 19,000 miles have come in one of the coldest winters on record. This will be my first full summer with the car. If I could even get to 10 cents per mile, I would be ecstatic.


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## spacedout (Dec 7, 2010)

plasticplant said:


> Since I bought the car in mid Aug, diesel has been anywhere from $3.79 - $3.99. Its been holding strong now at $3.89. Fuelly says I'm at 10.8 cents a mile. I very happy with that, as i am not a hypermiler and enjoy using the power this car offers. I think that number will start to drop now, as most of my 19,000 miles have come in one of the coldest winters on record. This will be my first full summer with the car. If I could even get to 10 cents per mile, I would be ecstatic.



My 1LT 15.6 gallon tank if on empty is $50-60 to fill with premium gas at a similar average of $3.79-$4.10. My cost per mile over 43K miles is 10.8cents, I have no doubt you can beat that with a full summer averaged in. 

My lowest cost per mile running $3.45 a gallon gas getting 37mpg average for the month was 9.3cents per mile.


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## money_man (Feb 25, 2014)

I'm about 5.50/ american gallon


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## obermd (Mar 3, 2012)

money_man said:


> I'm about 5.50/ american gallon


Out of curiosity, how much of that is taxes? The reason I ask is because between the US Government and Colorado I pay less than 50 cents a gallon in taxes.


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## money_man (Feb 25, 2014)

Well I'm in nova Scotia. We pay roughly $0.80/gallon in taxes. It breaks down where the cost per liter comes from on some pumps, I'll snag a picture next time I see it.


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## diesel (Jun 8, 2013)

I always add an extra gallon. Doesn't take but a minute and worth the extra 50 or so miles I can go.


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## warloc (Dec 10, 2013)

FYI, after a couple of times that I intentionally put in as much fuel as I could get in the tank I've had a CEL come on for anywhere between 50 and 100 miles and then go out. My wife fills up until the pump shut off and does not add any additional fuel, never had the CEL come on after her fill up. She gets the job filling her car. I wonder if anyone else has had this happen? I may have to start a new discussion on this topic.


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## money_man (Feb 25, 2014)

Prob vent/solenoid acting up.


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## LemonGolf (Feb 17, 2014)

money_man said:


> Prob vent/solenoid acting up.


Can you please give details on this vent/solenoid?


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## money_man (Feb 25, 2014)

There's an emission system that has a charcoal box. If you top up to many times this can swell and stop the tank from venting. Resulting in a cel


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## BradHerr (Sep 29, 2013)

Does the diesel use a charcoal canister? 


-Brad


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## money_man (Feb 25, 2014)

Was told by numerous people that the diesel cruze doesn't have the canisters or vents so it can be filled up the neck.


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## KpaxFAQ (Sep 1, 2013)

Well I just said **** with it and took my time at the station. Pump clicked at 11.5gal, I was able to slowly fit 3 more gallons in for a total of 14.5gallons! It was complete liquid to the lip of the neck at that time. Not worth it for everyday filling up but if I had long daily commutes heck yeah I'd do it. 

Sent from AutoGuide.com Free App


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## LemonGolf (Feb 17, 2014)

I filled up my CTD for the first time yesterday evening with the level a bit under a quarter tank remaining. Throughout the entire fill-up, I dribbled the fuel out of the pump as slow as it would go and nearing the end I heard the fuel, or so I thought, gurgling as it rose up the tank and into the filler neck. When I removed the pump, I saw foam receding back into the tank. At the rate I pumped, I'm surprised the fuel foamed as much as it did. It was dark out so I wasn't able to see what the level ended up at by the time the foam settled, but I do wonder how much foaming (height?) actually occurred. I ended up pumping 12.3 gallons at the first click-off and did not add any more. My gauge showed my tank completely full.


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## Sperry (Aug 3, 2013)

I think the fuel neck was made bigger because diesel foams so much.. That's the only thing I can think of that might answer the capacity difference.. It foams even while filling slowly with a gas can..


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## catbeard (May 4, 2014)

I fill mine up till its standing at the top of the neck almost pouring out, it just takes time for the foam to die down and I've had no problems. I can drive two days without the gauge moving and it says I have dame near 700 miles to E.


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## Danny5 (Dec 22, 2011)

I always add an extra gallon. Takes a few minutes of course. No matter how slow I fill up, I always get foam


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## spaycace (Feb 9, 2012)

a trick I try to employ when filling up my tank is to try and find a station that has your vehicle parked slanted downhill and away from the pumps. I was able to fill up and extra 2.4 gallons after shutoff on my Acadia! My Volt and G8 are a little less forgiving in that regard, and apparently shutoff a lot later in the process of filling up. Using that same trick on those 2 vehicles, I usually only get an extra .5 to .7 gallons in the tank. I too fill up before I have to drive somewhere as often as possible, or at least 10-15 miles from home. Pumps definitely make a difference as well, as I used to have to go to certain stations to fill up the Eco to full, and it took a good 10 extra minutes to do so! As for diesel foam, I'd look for a conditioner of some sort to minimize it, but having grown up on a farm, I know you can't really ever get rid of it completely when filling up, no matter how slow you go, because it's created coming out of the nozzle, as well as splashing into the tank.


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## TeckyWalla (Aug 30, 2019)

A friend was using the practice of filling tank to the max, after getting warning come up on several occasions, it was found to be bad practice.
Quote:
"Gas topping can damage your car’s vapor collection system, designed to reduce harmful emissions and manage fuel vapor.

Overfilling the gas tank can cause liquid gas to enter the charcoal canister, or carbon filter, which is designed only for vapor. Gas in the system can affect your car’s performance by causing it to run poorly, and cause possible damage to the engine"
TW..


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## Rivergoer (Mar 30, 2017)

TeckyWalla said:


> A friend was using the practice of filling tank to the max, after getting warning come up on several occasions, it was found to be bad practice.
> Quote:
> "Gas topping can damage your car’s vapor collection system, designed to reduce harmful emissions and manage fuel vapor.
> 
> ...


True for Gas vehicles but this is a Diesel thread...


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## sailurman (Sep 29, 2016)




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