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Posted from: http://www.epa.gov/donttopoff/
Don't Top Off Your Gas Tank!
HELP PROTECT THE ENVIRONMENT!
SAVE MONEY!


* Do you top off your gas tank and overfill it?

* When the gas pump nozzle clicks off automatically, do you add a little more gas to round off your dollar sale?

* Topping off your gas tank is bad for the environment and your wallet.

Here's why:

Topping off the gas tank can result in your paying for gasoline that is fed back into the station's tanks because your gas tank is full. The gas nozzle automatically clicks off when your gas tank is full. In areas of ozone nonattainment, gas station pumps are equipped with vapor recovery systems that feed back gas vapors into their tanks to prevent vapors from escaping into the air and contributing to air pollution. Any additional gas you try to pump into your tank may be drawn into the vapor line and fed back into the station’s storage tanks.


Gasoline vapors are harmful to breathe. Gasoline vapors contribute to bad ozone days and are a source of toxic air pollutants such as benzene. Evaporation from the spillage of gas from overfilling can occur, contributing to the air pollution problem. Remember you pay for the gas that evaporates or is spilled on the ground.

You need extra room in your gas tank to allow the gasoline to expand. If you top off your tank, the extra gas may evaporate into your vehicle’s vapor collection system. That system may become fouled and will not work properly causing your vehicle to run poorly and have high gas emissions.


Topping off your gas tank may foul the station's vapor recovery system. Adding more gas after the nozzle has automatically shut off can cause the station's vapor recovery system to operate improperly. This contributes to the air pollution problem and may cause the gas pump to fail to work for the next person.

only if you know you'll burn that gas immediatley is when you should top off, when wayne knew he had to travel more than a 1000 miles to his destination.

For my car parking at night makes the gauge goes below half, but in the morning when it has sitted in the sun all nice and toasty the fuel gauge spikes over half again! Wee free gas.

I Let the pump shut off and then round to the nearest dime. Sure don't get much more

I Let the pump shut off and then round to the nearest dime. Sure don't get much more

Same here.

I completely agree with the OP. Trying to squeeze in a bit more gas in is a fools game. When the pump clicks off, dub it done.

Another fools game: running your tank dry.

Hi Mendel:

___I will disagree. Not topping off means yet another wasted trip into a gas station to refuel. Those extra 1 to 4 gallons over 4 tanks can allow one less stop every 4 or 5 tanks.

http://www.cleanmpg.com/photos/data/523/First_Tank_Top_off_and_795_DTE.jpg
2011 Ford Super Duty

http://www.cleanmpg.com/photos/data/523/2010_KLX_250SF_Inital_Top_Off_Collage.jpg
2010 Kawasaki KLX250SF

http://www.cleanmpg.com/photos/data/523/Final_top_off_in_Long_Island.jpg
2009 BMW 335d

http://www.cleanmpg.com/photos/data/523/Second_Top_off.jpg
2010 Prius-III

http://www.cleanmpg.com/photos/data/523/Final_topped_off_fill.jpg
2008 HCH-II

http://www.cleanmpg.com/photos/data/523/Yamaha_XT_250_Review_-_Top_off.jpg
2008 Yamaha XT250

http://www.cleanmpg.com/photos/data/523/Calibration_Tank_Top_off.jpg
2009 Corolla XRS

http://www.cleanmpg.com/photos/data/523/Diesel_Top_off.jpg
2007 Civic iCDTi

http://www.cleanmpg.com/photos/data/530/Topped_Off.JPG
2001 Honda Insight

___As just a few.

___Good Luck

___Wayne

I top off as best i can too but i drive a diesel so there is less of a worry about vapours. It foams like hell though and it can take some time to fill it right up. I could have 6 or 7 litres to go when it would click out. That's pretty excessive imo.
Still though, i wouldn't mind knowing how exactly the vapour recovery system works. I was thinking this recently as the pump nozzle was enveloped in foam while i topped off the tank. I pulled the nozzle back out a little so it wouldn't rob my foam!
"Thats my foam! I paid for it!!" lol

ollie

Hmm... how is it a fools game? Letting the pump determine my fill means 380 miles until I see the flashing pip (fill up in 30 miles, or else, more or less). When I take the time to fill to what the tank can actually handle, my range is 540 miles until I see the flashing pip. I dunno about you, but 380 miles won't see me through a week, but 540 will.

As much as I would like to have a 600 mile range, I'm content to let the pump click off and deal with 350-500mi depending on how stretchy the bladder feels. There have been multiple reported $1000 Prius tank replacements due to fouled evap systems from overfilling. It might be a small risk but it still isn't worth it to me.

Then there's what I saw last weekend on the Mass Pike. I pulled into west-bound Lee rest stop behind a Nissan Sentra (no surprise...he had passed me at 15+ over the PSL not too far back) and we started filling at about the same time. I got out, pumped my 7 gallons, got back in, wrote down my numbers, and saw that I was boxed in and had to wait for the guy. And wait. And wait. And wait.

The reason for the wait was that he kept on topping off the tank click after click after click after click. Eventually I noticed the vapors start to pour out of the filler neck past the nozzle's emissions control. Maybe 15 seconds after that this jackass actually had gasoline pouring down his paint. I was going to politely (probably not) point this out but I guess he decided that was enough and put the nozzle back.

So guess what I got? A cabin full of fumes! Captain Click took off ahead of me with a hydrocarbon trail that just wouldn't quit...he must have had liquid gas pouring out the breather line or something.

So you guys do what you want. Personally I'd like to make use of my car's PZEV feature. (Obviously this isn't really a problem for diesel people...one considerable benefit of low-volatility fuel.)

Hmm... how is it a fools game? Letting the pump determine my fill means 380 miles until I see the flashing pip (fill up in 30 miles, or else, more or less). When I take the time to fill to what the tank can actually handle, my range is 540 miles until I see the flashing pip. I dunno about you, but 380 miles won't see me through a week, but 540 will.

Just doing a little rough math: say your tank capacity to the pump shut-off point is 40 liters (sorry, Canadian, I'll convert at the end). Just going by your range difference, 540/380, You appear to have nearly 17 liters (nearly 4.5 US gallons) worth of capacity in your tank filler pipe.

Wayne,

I figure our tank filler pipe might have 1 liter (optimistically). Our tank's 45 liters. If I run it till the warning comes on, it takes about 37 liters. So with that liter in the neck I'm neglecting to fill, I'm filling 1/37 more frequently than I should be. Now, our fillups almost invariably coincide with my wife dropping off some mail, I roll another 100 yards to the station, on weeks we need to fillup.

All-in-all, this is not having a big impact, particularly balanced against possible spillage.

Hi Mendel:

___It's not just the filler neck but first click can have fuel rising into the filler neck (that is what happens) while the tank is not even close to being filled.

___Good Luck

___Wayne

Just doing a little rough math: say your tank capacity to the pump shut-off point is 40 liters (sorry, Canadian, I'll convert at the end). Just going by your range difference, 540/380, You appear to have nearly 17 liters (nearly 4.5 US gallons) worth of capacity in your tank filler pipe.

Wayne,

I figure our tank filler pipe might have 1 liter (optimistically). Our tank's 45 liters. If I run it till the warning comes on, it takes about 37 liters. So with that liter in the neck I'm neglecting to fill, I'm filling 1/37 more frequently than I should be. Now, our fillups almost invariably coincide with my wife dropping off some mail, I roll another 100 yards to the station, on weeks we need to fillup.

All-in-all, this is not having a big impact, particularly balanced against possible spillage.

The problem is the Prius is overly sensitive to heat/cold/(humidity??) when filling. As Brick mentioned, there's also the emissions saving twaddle on the Prius that tends to cut the fill off extremely early. The first shutoff is never anywhere near the neck of the tank. If I have an 11.9 gallon tank, than I want to use at least 10 to 10.5 gallons of that capacity. This does not happen in the Prius unless you go out of your way fill beyond the automatic shutoff. I have yet to see, however, fuel sitting at top of the filler opening when I get done fueling. I've just been filling to what the scangauge predicts the amount of fuel used, and sometimes a bit over.

How many people have a series of photos on their computer composed of "gas-filled car holes"? Just Mr Wayne.

Anyways, once the pump clicks off, I reapply gas slowly till the 2nd click. Sometimes the pump clicks off a few gallons early and going till the 2nd click adds another 3 or 4 gallons. Most of the time though going to the second click doesn't add more than 0.2gallons.

Hi Justin:

___Of the 6,000 + pics I have uploaded to the gallery, there are 120,000 that are stuck on my HD's. With that many pics of review vehicles and events, a few odd top off fills are bound to be taken. You should see my gas station price shots ;)

___Good Luck

___Wayne

I think that the reason that some of us top off all the way is to get an accurate reading from fill to fill. It is the only way I know of getting an exact fill to fill mileage.

How many people have a series of photos on their computer composed of "gas-filled car holes"? Just Mr Wayne.

7 words for you Justin, "You know you are a hypermiler when...":D

I think that the reason that some of us top off all the way is to get an accurate reading from fill to fill. It is the only way I know of getting an exact fill to fill mileage.

Same here! On the Crawler, first click is almost THREE GALLONS short of "full." At my FE and tank size, that's about 20%!

Hi, Nevyn -- check out the fill level on my record tank in the Elantra. ;)

Hi, Nevyn -- check out the fill level on my record tank in the Elantra. ;)

I wonder if you had a 16 gallon tank? Mine's 14.5. How far can I push it with the low fuel light on, if it's full to 'Wayne level'? I'm scared to try.

No, mine is marked at the same 14.5g yours is. This is understated a bit as I did use over 15g once before I began stuffing, so Hyundai has built in a "safety margin."

As for how far you can go... 17g is it. I was coasting in FAS around a corner when I bump started... and the engine wouldn't do anything but idle when I pushed the pedal. :eek: It had been giving longer and longer hesitations before responding to accelerator application but I tried 3 times and got nothing but idling that time. (I presume this is due to low fuel pressure.) So... I shut it off again, pulled a U-turn and coasted up to a pump at the gas station I had just passed.

That's right, I did all the hard work for you. ;)

Hi Mendel:

___It's not just the filler neck but first click can have fuel rising into the filler neck (that is what happens) while the tank is not even close to being filled.

___Good Luck

___Wayne

How about when filling up, slowing down the pump for the last couple of gallons to make sure that you don’t trick the sensor into thinking the tank is full, and as you get the first click go another click. I just switched to this myself, I used to always fill to the max, but had a slight overfill once and decided that may not be the best way to go. Another thing I do, most people think I must be crazy, is lift the hose before finishing to make sure I get all the fuel I paid for.

Anyways, once the pump clicks off, I reapply gas slowly till the 2nd click. ... Most of the time though going to the second click doesn't add more than 0.2gallons.

Same here. I do that so I can fill the tank rapidly on the max rate setting, then finish at a consistent fill level by giving it a few seconds to quit bubbling and run the pump at its slowest rate till the next click. I've never gotten more than 0.3 gallons more in that way, and usually it's about 0.1.

I have had problems in the past with several vehicles that would leak or overflow when filled to the cap, and I worry about "waterlogging" the charcoal canisters with gasoline when that's done.

Wayne, doesn't topping off still risk fouling the evap canister? That could have a huge impact on emissions.

Here in Oregon, topping off became illegal as of Jan. 1 this year. Unlike in most states this is easily enforced because it is also illegal to pump your own gas and only attendants are allowed to do it.

All the above is for gasoline filling only. Diesel doesn't produce the same kind of evap emissions, and though most Oregonians don't realize it we are allowed to pump our own diesel.

Hi Dan:

___There is a "risk" but in over maybe 1,200 top-offs in over maybe 250 different vehicles over the past 30 years, I have never had a problem with any evap canister.

___Regarding the Oregon law about an attendant filling... When we ran the 48-Contiguous State WR, we had to top off in OR as that was our starting state. The Attendant was there but we told him what we were doing and he said have at it.

___Good Luck

___Wayne

Regarding the Oregon law about an attendant filling... When we ran the 48-Contiguous State WR, we had to top off in OR as that was our starting state. The Attendant was there but we told him what we were doing and he said have at it.Wow, you're lucky. I've never had much luck convincing an attendant to let me pump it, and heaven knows I sure tried the first couple years I lived here. Believe it or not and as stupid as it sounds, you actually could have been cited for pumping your own.

Probably helped to be in a small town, where the attendants don't care as much about the rules -- including the new top-off law, from what I'm seeing so far.

How many people have a series of photos on their computer composed of "gas-filled car holes"? Just Mr Wayne

I was pondering that too ;)

In our municipality, it's illegal to have self-serve stations. Full serves tend be strong proponents of topping-off, 'cause, well, money I'd guess: they've got you, might as well cram as much as possible in there. North Vancouver was another district with the same rules, but they have now caved in to sanity, full serves are like dodos everwhere but our berg. Anyway, my wife's mail drop off is just down the road in a neighbouring municipality, so...

No, mine is marked at the same 14.5g yours is. This is understated a bit as I did use over 15g once before I began stuffing, so Hyundai has built in a "safety margin."

As for how far you can go... 17g is it. I was coasting in FAS around a corner when I bump started... and the engine wouldn't do anything but idle when I pushed the pedal. :eek: It had been giving longer and longer hesitations before responding to accelerator application but I tried 3 times and got nothing but idling that time. (I presume this is due to low fuel pressure.) So... I shut it off again, pulled a U-turn and coasted up to a pump at the gas station I had just passed.

That's right, I did all the hard work for you. ;)

So wait...you're seriously saying that I have 80-90 miles after my low fuel light comes on?

I don't remember how far past the low fuel light it is, but I can tell you I've had the needle about 3 widths under the E line without running out.

I've filled nearly every vehicle at every fill-up to the very top because I have always logged them for tracking. I have not had one trouble with evap because of it.

You may have more to worry about if you filled with gas, didn't drive, and allowed the fuel to warm up than worrying about the actual level. If you fill and then drive it should be no problem.

I always top off. Well, usually.
I usually fill up at Sams. And those pumps tend to have a very early cut off. I can easily get 2 gallons more in...sometimes closer to 3. That's easily another 90 miles (and hopefully more) I can go. For my usual route, that can be an extra week without refilling.

Whereas I noticed at other gas stations, the cutoff is much later. In fact, at one Exxon (or is it Mobile?), it cut off right at the top. So it seems every pump is different. And I make sure to top off slowly and carefully.

-Mike

The click off point can vary by up to 6 gallons depending on the side slope angle that the car is sitting at when filling my tank. It has a 10.9 gal tank, but can click off at 8 gal when the fill tube is on the downhill side of the car and as much as 16 gal when it is on the uphill side of the car. I try to gas up at the same pump, or at least a similar slope angle when gassing up to keep the gas log from varying too much.

Where are you finding gas stations with a side slope by the pump? All I've seen for years are on a quite level pad.

Got a bunch of 'em around here; the pad isn't very large and they slope pretty sharp with one set of wheels off the pad. Some of 'em don't have pads.

All of the bigger, newer stations are flat, but there are several small 2 pump gas stations around here that have a significant amount of side slope on the paving next to the pump island.

Even though it is the level that stops the fill, it directly has much more to do with the flow rate than anything else. (ultimately the level) Many of them will not shut off if on low setting or the flow rate is very low.

Just filled up yesterday, always go to the second click (first time I used AC about 30-40% of the time) and the results were actually really good - 53MPG. Did not notice at the time, but now I am wondering if it was an early shutoff as the scangauge was showing 8.5Gal of gas used vs 7.8 per the actual fillup. This was also my first fillup durring the hotter part of the day (95 degrees). Then again the last gallon countdown had not started, so will have to see on the next tank. If the results are accurate, I may not take a huge hit to FE during the summer.

My fills are first click, which gives me MORE accurate tank to tank readings than topping off. Why? Because any of the 3 drivers in our house could fill any of our 3 cars, and only I would be willing to truly fill. So, while there is some variation at first click, it is consistent with the prior fill.

The alternative of topping off when I start a drive just results in MORE trips to the pump, and prevents consistent measurement of the preceding and/or upcoming driving using other fill methods.

Also, I don't ever want to overfill, and tanks tend to last me a long time anyway. My daily driver will go 2-3 months on a fill (the CRV). Plus, looking at my logs, I'm not seeing significant fill error anyway.