Tech

Every time I fill up, those last two gallons (8 or 9 liters) take forever to top up and it is frustrating. By that I mean the gas pump cuts out and I can still ease another 8 to 9 liters into the tank although it is slow going. Does everyone experience that?

I filled up yesterday. The fuel gauge was just touching the red indicator on the fuel gauge and it took 60.494 liters or 15.98 US gallons, the advertised size of our gas tank. Yet the mileage remaining indicator said I was good for another 25 kilometers or 15 miles. At that, I had done 699 kms or 434 miles. I wonder if the gas tank isn't a tad bigger.

Gadgetjq

You're really not supposed to keep filling after the nozzle clicks off (unless you're using a particularly sensitive one). There's expansion space built into the tank and the evaporative emissions system. If you add too much fuel there's no place for it to go but into the charcoal canister and vacuum tubing. If that happens you could wind up replacing some expensive parts at worst or dealing with error codes at least.

If you think the nozzle(s) at your normal gas station are too sensitive, try another place just to see if you take on more fuel after the low fuel warning light comes on.

Cheers!

Brown13

"Topping off" the gas tank is just asking for trouble!

horseshoez

iTrader: (2)

If you keep milking fuel into your tank, sooner or later you're going to have to foot the bill for an expensive EVAP repair. Not sure where you are, but in many localities it is illegal to top the tank off like you do.

WheelMcCoy

Are you filling up on a flat surface? One station I fill up is on a slight incline. When my car is pointed downhill, more gas goes in... pointed uphill, less gas goes in... before the pump clicks off. I don't try to top off for reasons mentioned in other comments.

jcross1231

Foaming in the tank often stops the fill a gallon or so before the tank is full, especially if you've got one of those all-or-nothing nozzles that has no intermediate setting. If you fill to the bottom of the fill tube, there's still plenty of expansion space.

Tech

Well I'd have to see a diagram to verify that.

If the fuel level needle is on the red line as it was in my case, then I should be able to pump 60.5 liters (16 US gallons) of fuel into the tank which is what the specification states. That is if the needle is accurate. If there is still usable fuel left in the tank when I am on the red line to the tune of 8 or 9 liters at that point, then that might explain it.

Anyway, I've never had an evaporative issue in any of my cars and that would include the CR-V that I owned for just shy of 15 years.

horseshoez

iTrader: (2)

Yup, you can lead a horse to water...

Good luck with your evap.

kurtatx

Liquid gasoline is not the only thing in your gas tank that has volume. The gasoline fumes also take some of that volume. Those fumes are critical to proper engine function. As others have said, your EVAP system will try to compensate and shit the bed.

More of the story: Don't be an idiot.

markAZ

Uhh, no, it doesn't work like that. The evap system is intended to prevent gas vapor from escaping into the atmosphere, it's an anti-pollution device. The charcoal canister collects vapor and then releases it into the intake system of the engine. It doesn't compensate for anything. And gas vapor in the tank is not critical to proper engine function, probably quite the opposite.

Overfilling the tank can result in liquid fuel getting into the charcoal canister & saturating it so it can't absorb vapor. It can then dump fuel into the intake and cause the engine to run poorly.

As for the capacity of the tank vs. the gauge, most car makers will show empty when there's still a couple gallons left. Its partly to help prevent running out of fuel and to protect the fuel pump that is cooled by the gas it's immersed in. It's not good to run fuel injected engines out of fuel. Plus, gas gauges are often not terribly accurate in the first place.

MyGuti

I don't know about newer model cars.....but I've been topping off like the OP for years now, on my 07 base and type-s, zero issues to report...and a bit more mileage.....

horseshoez

iTrader: (2)

The previous owner of our Accord used to milk the tank full to the brim; about a year later I had to replace much of the EVAP system.

Long story short, filling the tank to the brim is bad for the environment (prevents the EVAP system from doing it's job), bad for the EVAP system, and ultimately, bad for your wallet.

thoiboi

How do you figure?

Tech

As I already mentioned, I had done so on my 1999 Honda CR-V and I had it for almost 15 years, then on my 2013 VW Jetta TDI and now the RDX. BTW, zilch repairs to any engine system on any of them.

The fact that I filled it with 15.98 gallons (yup, the specified size of our tank) with the needle on the red indicator of our gas gauge tells me two things. Either the tank was empty and it took the specified 16 gallons, or the tank still had 2 gallons of gas left in it when the needle was on the red indicator.

chickdr

If you put 15.98 gallons in the tank it obviously didn't have 2 gallons left. In my experience when the range shows 0 miles, it still has a decent amount of fuel left. I have yet to put 16 gallons in when filling even when the needle is at empty.

Tech

Unless you have run it empty, how would you know? I don't really want to run it empty.

WheelMcCoy

My experience with my 2012 TSX Wagon:

1. The needle on the red line fuel gauge isn't accurate, but it's a good warning.
2. The range calculation in the multi-information display is only an estimate based on past trips.
3. The Low Fuel indicator light in the instrument panel is the best tool, and alerts me when I have 2.8 gallons (10.5 liters) remaining in the gas tank.

Check your owner's manual for the reserve capacity in your vehicle.

RenoTL

I think we are missing the OP's problem here. Regardless of your feeling about "topping off" or "not topping off", when filling a car, the gas pump should not be cutting off when there is 2 gallons left to fill in the tank. The Evap system doesn't need 2 gallons of room. I don't know what the problem is but this does not sound normal to me.

horseshoez

iTrader: (2)

It depends upon the shape of the tank; some tanks require more than two gallons, some far less. What makes you think the tank in the 2G RDX needs less than two gallons?

MyGuti

if I stop pouring fuel in the car when the pump cuts out....that will result in less fuel, which results in less mileage per tank. Since I can usually get another 10bucks or so of fuel after cutoff = more fuel = more mileage (unless I change my driving habits each fillup)

RDX-Rick

If you always stop pumping gas when the tank reaches the same level, whether that is 14 gallons or 16 gallons, then your mileage calculations will always be accurate .

For example, if you always fill up to the 16 gallon mark, and you drive 320 miles, your mileage is 320/16 or 20 MPG. However if you always fill to the 14 gallon mark, your distance traveled will drop to 280 miles, which is 280/14 or exactly the same 20 MPG.

A problem with accuracy develops when you fill-up to a different point each time. For example, if you fill up to the 14 gallon mark at one fill-up, and drive 280 miles until your empty, then if you add another 2 gallons (fill-up with the full 16 gallons), your mileage calculation would be 280/16 or only 17.5 MPG. So forcing more gas into the tank results in a lower mileage calculation.

Now that we have determined that filling to a consistent level each time is required for an accurate mileage calculation, we need to determine the best method of consistently filling up to the same level each time. Since different pumps will shut off at different levels, stopping when the pump shuts off, doesn't seem to be as accurate as topping off to the brim, which would be the same every time.

However we know that overfilling a tank can cause liquid gas to get into the charcoal canister, rather than gas fumes which it was designed to handle. Because of this danger, I would not re-fill to the brim just to get accurate mileage calculations. (at least not any more).

I have recorded every gas fill-up since I purchased my 2016 RDX (127 fill-ups to date). I calculated the mileage using MILES/GALLONS and I also recorded what the trip computer said. After all those fill-up I discover the average error between the Trip-Computer and the Math was 4.9%. Sometimes there was only a 0.5% error, and other times it went as high as a 10% error. By the way, I was filling to the brim to get accurate calculations.

My conclusion is that filling to the brim will provide the most accurate calculations, but due to the risks, I would consider the value on the trip-computer as an acceptably accurate result.

MyGuti

sounds good, this topic has possibly deterred me from filling to the brim.....I may only add an additional 5 dollars after cut off, opposed to the 10......really don't want to compromise my EVAP system as I plan on keeping my cars for the foreseeable future

chickdr

When the range has read zero, I have driven at least 10-15 miles before filling up and still never put 16 gallons in. No way to know exactly how much gas was in the tank.

MHarnois

You're confusing mileage with fuel consumption. By mileage he means distance he can achieve with one tank which is the correct definition of mileage; more fuel in tank equals more miles driven. You on the other hand are talking about miles per gallon consumption.

horseshoez

iTrader: (2)

I would argue you are the one confusing the terms.

From Dictionary.com

RDX-Rick

I think you are describing "Range", which is the distance that can be traveled with the fuel remaining in the tank. For example the RDX's MID displays a "range" estimate which shows an estimate of the distance you can drive before reaching empty. It is constantly being updated depending on the current fuel consumption rate, or "mileage". Topping the tank up to the brim will provide a greater "range" than just refueling to the point when the pump shuts off.

MHarnois

Thanks for making my case. If the first two definitions were not enough, let's understand the third one:

"the number of miles or the average distance that a vehicle can travel on a specified quantity of fuel"

Increasing the specified quantity of fuel will increase the average number of miles that the vehicle can travel, therefore more mileage after refueling. This of course has no impact on MPG which the OP doesn't claim either.

horseshoez

iTrader: (2)

Quite the contrary, you cannot make case relative to a "tank" as that is in no way a specific amount of fuel. The fact is, pumps click off at different points where there can be a delta of as much as a gallon from one pump to the next. The only context where the term "mileage" comes into play here is the number of miles driven per gallon.

MHarnois

Exactly, that's what the OP (MyGuti) is talking about, more fuel in the tank by topping off gives him more range or more mileage, not better MPG as others have tried to read in his comment.

MHarnois

Dude, come on! Not knowing specifically how many gallons you're starting with, will you go further if I always give you an extra gallon?

horseshoez

iTrader: (2)

Kindly don't "dude" me; the discussion here is the word "mileage". When correctly using this noun, one is typically referencing "miles per gallon".

MHarnois

You posted the definition and yet you don't understand it. Just trying to help you out.

horseshoez

iTrader: (2)

No, I understand perfectly, you are using the term "mileage" incorrectly.

TacoBello

Seriously... listen to the words of the wise in here. Stop pumping gas when it clicks off.

You may have gotten away with it for years. Older cars seem to not have been effected the way newer ones are. Either way... it's no joke. It will eventually cost you. There have been members on AZ that have gone through the same thing and it was an expensive lesson for them to learn. Don't be like them.

and honestly, what's the difference if you get 500km to a tank, or 600km? You're still paying for that extra 100km either now, or later. The only difference being is you maybe drive two days longer with that extra bit of volume. If this is coming down to a debate about not wanting to step out of your car for 5 minutes, once every 7-14 days, well...

thoiboi

Ya'll effectively arguing speed versus velocity


i think MyGuti was using "mileage" in the non MPG sense. As in, "i can go farther 'on a tank'".. Well yeah, no shit, if you fill it to brim, you'll go farther before you have to fill up again because there's more gas in there.. But in the MPG sense of the word (which most people refer to as 'mileage' colloquially) I wouldn't see the difference.

now both of you.. back to the matter at hand.. STOP TOPPING OFF. Or if you do, do it, I don't care.. Just don't suggest that everyone else top off.

MHarnois

I'll try one more time as English is a funny language where definitions don't always seem to matter. There are at least two ways to get better mileage with your car:

1- Increase the tank volume, and you will cover longer distances per fill, hence better mileage. E.g., 300 miles driven with more fuel is better mileage than 250 miles with smaller tank.
or
2- Increase the car's efficiency, and you will get better MPG allowing you to cover longer distances with same fuel, hence better mileage. E.g., 500 miles driven at 25 MPG is better mileage than 400 miles at 20 MPG with same tank volume.

I do understand how some people over time equate mileage with MPG but they really are two different things.

RDX-Rick

According to Merriam-Webster, either definition is correct.............

Definition of mileage

1: an allowance for traveling expenses at a certain rate per mile


2: aggregate length or distance in miles: such as
a : the total miles traveled especially in a given period of time
b : the amount of service that something will yield especially as expressed in terms of miles of travel
c : the average number of miles a motor vehicle will travel on a gallon of gasoline that is used as a measure of fuel economy,
"gets good mileage"

3a : usefulness
got a lot of mileage left in it

b : benefit derived from something
got good political mileage from the debates

Since the OP did not object when I said "filling to the brim" would result in less mileage, I assumed he was speaking about fuel economy, or MPG.

Personally, I would use the term "range" to describe how many miles a car can go on a tank of gas ( or the remaining gas in the tank), and would use "mileage" to describe how many miles a car can go on a single gallon of gas. But then I'm Canadian, not English..

horseshoez

iTrader: (2)

Agreed, and by definition (see above), mileage is "miles per gallon".

chickdr

Actually if you read the WHOLE M-W definition above BOTH of you are correct. Now I will give you that in today's vernacular, "mileage" typically equates to MPG, but as referenced above the definition allows for both total distance traveled and MPG. So, lets just agree both of you are right and stop the pissing contest...

horseshoez

iTrader: (2)

From a strict interpretation, you are incorrect. Why? Because the whole "distance traveled" element is relative to a precise amount of fuel consumed; something which is not possible when starting with a "tank" of fuel.