Why Topping Off won't kill your truck

[710-oil-614]

I can answer your questions with certainty.

Gasoline expands 0.069% per degree F.

Or 1% per 15 degrees F if you prefer.

Rounding the tank size to 15 gallons, one needs to burn 0.15 gallons on the first drive cycle to make room for 15 degrees of temperarure rise, or 0.30 gallons for a 30 degree rise to be 100% safe.

I will add though, due to physical size and shape, even after 3 clicks, or 5, your tank will not be 100% full. You really can't get them 100% full. By design. Thank your EPA for that.

I will thank the EPA for it because emissions controls are a great thing.

You seem very agitated by the extra half gallon you can or can’t squeeze into a tank.

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[Glen Baker LLC]

That's what the yellow triangles are for in that book likely found in your glove box.

Did AI draw that?

Now, why would I want to break the seal on my perfectly pristine owners manual, that I keep in my glove compartment?? Unless necessary.

It is already downloaded on my phone and tablet.

That's how I roll.

 

[The Real Maverick]

Now, why would I want to break the seal on my perfectly pristine owners manual, that I keep in my glove compartment?? Unless necessary.

It is already downloaded on my phone and tablet.

That's how I roll.

As the new kids say:

kewl

 

[Mark S.]

I will add though, due to physical size and shape, even after 3 clicks, or 5, your tank will not be 100% full.

Is this speculation, or do you have some evidence? How much empty space will remain in the tank after 3 clicks? Or 5 clicks?

You really can't get them 100% full. By design. Thank your EPA for that.

I think this is the nub of this discussion. Let's apply some logic:

The term "by design" includes some assumptions, among them that the user follows manufacturer recommendations. For example, Ford limits the amount of weight you may safely carry in the vehicle. Overloading (depending on how much) likely won't break anything, but you will without doubt compromise performance for critical safety parameters, such as stopping distance.

Back to the fuel tank. It's almost certain that Ford designs its fuel tanks with an understanding of thermal expansion, so the tank design must leave room for fuel expansion after a fill up. Ford tells us (in the owner's manual) to stop filling after the first click, which implies it has determined you retain enough expansion space under all likely operating conditions if you follow that recommendation. I believe it's logical to assume Ford confirmed this to be the case during vehicle testing.

With that in mind, it seems to me that adding fuel after the first click reduces the designed-in expansion space. How much? I don't know. I'm sure there's some "wiggle room," but I don't believe you have offered any data to tell us exactly how much. What is the danger if the fuel expands beyond available expansion space? In the owner's manual Ford suggests there is a fire danger, but what about damaging fuel system components? You argue the conventional wisdom to avoid overfilling to prevent fuel system component damage is overblown. That's certainly possible, but I don't believe you have made a definitive argument. In my opinion, without access to Ford's design parameters and test data these questions cannot be answered with accuracy.

People often make operating decisions that exceed manufacturer limits based on assumptions about engineering; designers MUST have "overengineered" whatever device or system in question to provide a safety margin. The problem with assumptions like this is that they are exactly that--assumptions. Without data, it's simply impossible to know if or how much of a safety margin exists and/or precisely how much you compromise it by exceeding a published limit. Without this data, it seems to me following manufacturer recommendations is the safest bet. Among other things, operating recommendations are meant to ensure the vehicle is operated with its design specifications.

 

[The Real Maverick]

Is this speculation, or do you have some evidence? How much empty space will remain in the tank after 3 clicks? Or 5 clicks?


I think this is the nub of this discussion. Let's apply some logic:

The term "by design" includes some assumptions, among them that the user follows manufacturer recommendations. For example, Ford limits the amount of weight you may safely carry in the vehicle. Overloading (depending on how much) likely won't break anything, but you will without doubt compromise performance for critical safety parameters, such as stopping distance.

Back to the fuel tank. It's almost certain that Ford designs its fuel tanks with an understanding of thermal expansion, so the tank design must leave room for fuel expansion after a fill up. Ford tells us (in the owner's manual) to stop filling after the first click, which implies it has determined you retain enough expansion space under all likely operating conditions if you follow that recommendation. I believe it's logical to assume Ford confirmed this to be the case during vehicle testing.

With that in mind, it seems to me that adding fuel after the first click reduces the designed-in expansion space. How much? I don't know. I'm sure there's some "wiggle room," but I don't believe you have offered any data to tell us exactly how much. What is the danger if the fuel expands beyond available expansion space? In the owner's manual Ford suggests there is a fire danger, but what about damaging fuel system components? You argue the conventional wisdom to avoid overfilling to prevent fuel system component damage is overblown. That's certainly possible, but I don't believe you have made a definitive argument. In my opinion, without access to Ford's design parameters and test data these questions cannot be answered with accuracy.

People often make operating decisions that exceed manufacturer limits based on assumptions about engineering; designers MUST have "overengineered" whatever device or system in question to provide a safety margin. The problem with assumptions like this is that they are exactly that--assumptions. Without data, it's simply impossible to know if or how much of a safety margin exists and/or precisely how much you compromise it by exceeding a published limit. Without this data, it seems to me following manufacturer recommendations is the safest bet. Among other things, operating recommendations are meant to ensure the vehicle is operated with its design specifications.

Testing over 20 fill-ups:

I normally let the pump stop on it's own.
Then after a short pause, restart.
This adds 0.1 gal. +/-
Restarting a second time, adds even less. Then I usually go about my business.

Three times, out of curiosity, I would slooooowly, being careful not to spill, add as much as it would take. Giving as much as 3-4 minutes of wait time for fuel to "settle". Even with all the extra time and effort, usually only 0.5 to 1 gallon would go in beyond that first click. As described above, 0.01 gallons of expansion space is required for each degree F of temperature rise.

I have also looked at 3D renderings of the fuel tank.

I am totally convinced it is no big advantage to do so. I am equally convinced if you, or your cousin Vinny does this while borrowing your truck, it will do no harm.

Group: Do not mis-interpret my passion for the truth as "emotion". It does not matter to me in the slightest what you do or don't do.

I received piece of mind from all my detailed investigations. I'm just trying to pass some of that piece of mind along to others. No need to freak out. There is nomagical perfect stopping point. It is apparent a wide range of variability is acceptable. As it should be.

Surely you'll agree no two refueling events are precisely the same.

Also, pumps in different states are different. Ones in "smog" areas tend to be prone to false shut-offs. If you are content with getting 90% of a fill (which usually still moves the needle to "F") wonderful. I'm not asking you to change a thing.

The net result will be some people will note their gauges come off of "F" in 10 or 20 miles. Some people will notice their gauges come off the "F" in 100 miles.

This is for information sharing.
Do what makes you feel good.

 

[Glen Baker LLC]

As the new kids say:

kewl

It is just more convenient to have access to the manual on my phone anywhere I am.
I don't have to run out to the truck and dig through the glove compartment for the manual.
The manual does not get taken out of the truck so it's always there if needed.

 

[Crash11]

This is just like a political debate. Nobody will change their mind.

For anyone who hasn't yet made up their mind, feel free to PM me if you're interested in what the EPA light duty vehicle testing group at NVFEL thinks.

 

[Mark S.]

Three times, out of curiosity, I would slooooowly, being careful not to spill, add as much as it would take. Giving as much as 3-4 minutes of wait time for fuel to "settle". Even with all the extra time and effort, usually only 0.5 to 1 gallon would go in beyond that first click.

This is anecdotal evidence. Your experience with your truck on those specific days cannot be extrapolated to all possible circumstances.

Do not mis-interpret my passion for the truth as "emotion".

I'm not sure why you felt the need to include this. I don't believe I accused you of being emotional.

No need to freak out.

??? In what way do you feel that I freaked out? I believe I offered a logical, reasoned argument for following manufacturer guidance.

Surely you'll agree no two refueling events are precisely the same.

Yes, which is yet another reason--I believe--that following the manufacturer's guidance ensures you never encroach on the designed-in expansion space enough to cause any issues.

It does not matter to me in the slightest what you do or don't do. I'm not asking you to change a thing.

No, but you are claiming it's okay to ignore manufacturer guidance. Extraordinary claims require extraordinary evidence. I don't believe you've supplied it, so I offered an opposing viewpoint.

 

[The Real Maverick]

@Mark S.

General comments. Not singling you out. Sorry if you felt that way.

 

[The Real Maverick]

This is just like a political debate. Nobody will change their mind.

For anyone who hasn't yet made up their mind, feel free to PM me if you're interested in what the EPA light duty vehicle testing group at NVFEL thinks.

TLDR

I predict it revolves around emissions.
(not vehicle damage or lack thereof)

If they are worth their salt, their test method would closely match what people do.

If you can post a short clip of RELEVANCE to three click-offs, that would be great.

 

[BAScott62]

I'm going 4 clicks next fill up. I'm a loner Dottie, a rebel

 

[HeyBales]

My 1st fill-up I did like I did in Rav4, which had a fill tube that could cause easy click-offs, and you could get more than 14.x gal tank.
And QT would slow down flow rate for subsequent auto-latches.
I'd normally hit 4 of those, seemed like after 4 they didn't slow flow down more so not useful. Get an extra gal that way.

That 1st fill up it actually did splash out the filler pipe on 4th latching.
Now, I was not holding lever as manual says since using the latch, but it was resting where it was supposed to according to manual which is no different than normal.
I don't think it was true overfill, but odd a splashing effect would be seen at end of fillup and not before during faster flow rate, there was enough that ran out had little puddle around drain hole, which made me wonder if the overflow to canister was inside neck like on Rav, and thought great way to start this off.
Decided then I'll just do 2 clicks unless I can hear the 1st one sounded like splashing early turn-off.
Just for consistency for getting MPG figures. 2 soft clicks.

Even if the manual is more like - "Give Me a Ping, Vasili. One Ping Only."

 

[todd92]

I've tried a 2nd click, at more than one station, just for the hell of it. Can never get even 0.1 gallon more in. Why does this thread have 5 pages and still going, when whether or not it's harmful, there's no point in doing it?

 

[Raymundo76]

Why "topping off" is OK as long as you don't spill and pollute.

(And why your car care nut and Uncle Joey have unfounded worries about the "carbon filter canister".)

I put "topping off" in quotes because it's really not possible to, even if you wanted to. So everyone can relax a bit if they want.

This thread is not meant to be a debate and I'm not telling anyone what they should or should not do.

This is information. Information that shows the risks of the past likely no longer exist today.

That said, in the hybrid with capless filler tube, I find it fills fully, reliably, repeatedly with just three clicks. No need to go beyond that.

Here is the fuel system diagram from Ford.

1: fuel fill tube
2: fuel module
3: fuel level sensor
4: fuel tank
5: fuel vapor return line
(5 is what people worry about needlessly)
6: fuel pressure sensor
7: refueling vent valve that opens when you push the refuel open door button
8: fuel tank pressure control during operation
9: carbon canister
10: vent valve
11: vent to atmosphere
12: vent to engine
13: recirculation valve
14: engine intake manifold

The particular technique different individuals use to refuel their trucks should have no effect on the much worried about "carbon canister".

Hope that helps some of you sleep peacefully. How that canister got ruined in a 1998 vehicle bears no resemblance to the hybrid Maverick of today

Some have reported damage to the valve with overfilling, so be careful.

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