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Panic buying, or shortage

Passion, instruction, buying, care, maintenance and more, any form of vehicle discussion is welcome here

Have you topped up with fuel in the last few days when you wouldn't have done normally?

Yes
7
8%
No
76
92%
 
Total votes: 83

pje16
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Re: Panic buying, or shortage

#447947

Postby pje16 » October 5th, 2021, 9:08 am

redsturgeon wrote:It is surprising how much fuel can be still in the tank when the fuel light comes on. When I get a new car I make a point of noting this figure. With my current car, I can still travel at least 80 miles once the fuel warning light comes on.
John


Agreed John
I can do around 60 "on the yellow" before I really panic (coast, and hope a lot of my next few miles are downhill !)
cheers
Paul

bungeejumper
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Re: Panic buying, or shortage

#447950

Postby bungeejumper » October 5th, 2021, 9:23 am

redsturgeon wrote:It is surprising how much fuel can be still in the tank when the fuel light comes on. When I get a new car I make a point of noting this figure. With my current car, I can still travel at least 80 miles once the fuel warning light comes on.

Oh indeed. Most cars can do 50 miles after the yellow light comes on. But two things:

Firstly, there's a deliberate silence from manufacturers on exactly how far you can go. It's an evil conspiracy, dammit, and they're trying to frighten you into not letting your tank get so low. If they ever spilled the beans, the roadsides would be cluttered with smart alecs who've muttered the fatal words: "Trust me, Mavis, I know what I'm doing. There's another four miles still in this tank...."

Secondly, do we really want to be running on the evil gunge that's washing up from the tank's sump? It killed my mate's fuel pump after he ran his Mondeo to a standstill, and the new pump cost him getting on for a thousand pounds. :o

I did once run right out, on a remote country lane with no mobile signal to summon help. (I hadn't been paying attention to the dash lights.) I set out on foot to find somebody with a petrol can, and in the end I made someone's day when I offered him a tenner for the contents of his lawn mower's tank. :lol: Pricey, but worth it for the lesson.

BJ

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Re: Panic buying, or shortage

#447951

Postby AWOL » October 5th, 2021, 9:26 am

bungeejumper wrote:
AWOL wrote:I feel no sense of panic (in either sense of overpowering fright nor of extreme anxiety). In fact I am often sitting at 5 or less miles of projected capacity when I fill up and it bothers me not.

Don't ever get a job as an airline pilot. :lol:

You're quite right to describe the half-tank-fillers the way you do. But running out of petrol on the road is a pretty awful thing, and it isn't so very surprising (at least, to me) that many people go to exaggerated lengths to avoid it.

The very least that people usually want to know is that they've got enough fuel for the next couple of days, or enough to pick up the kids from school, or enough to fulfil their work and social obligations. Or, indeed, to finish a long-distance journey that they've already started. I don't know about you, but I've certainly had the experience of driving on fumes in unfamiliar territory after two or three successive garages have turned out to be unexpectedly shut.

Or, indeed, there might not be any garages at all along my route. Or it might be Sunday, when some places are shut all day. Or it might be out in the wilds of France, where a lot of petrol stations are automatic card-only pumps and they don't necessarily accept British credit cards. (Been there, got the mental scars to prove it. :| )

In short, range anxiety isn't just for EV owners. I keep a couple of weeks' food in my kitchen, and I want to know there's a few days' juice in my tank. Waiting until I'm down to my last tin of beans isn't the way I want to play it. ;)

BJ


I ran out once in the 90s on the M5 when I hadn't noticed that I had turned red, joined the motorway and found myself on an incredibly long stretch without a garage. This did leave me overly cautious for a few years. I don't know if it is still like that (the long stretch without a garage on M5) or the psychology of the situation made the stretch seem longer but that wasn't nice.

These days I don't start a long trip without enough fuel for the journey with a little to spare. However I don't do as many long journeys so generally it's a case of not running on red too long. I don't like the idea of carrying the extra weight of extra fuel. I have grown very relaxed with having enough fuel for the circumstances and little more.

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Re: Panic buying, or shortage

#447952

Postby richlist » October 5th, 2021, 9:30 am

I remember reading somewhere that running out of petrol ie completely out.....damages the exhaust catalyst. Can anyone confirm ?

pje16
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Re: Panic buying, or shortage

#447953

Postby pje16 » October 5th, 2021, 9:38 am

pje16 wrote:
redsturgeon wrote:It is surprising how much fuel can be still in the tank when the fuel light comes on. When I get a new car I make a point of noting this figure. With my current car, I can still travel at least 80 miles once the fuel warning light comes on.
John


Agreed John
I can do around 60 "on the yellow" before I really panic (coast, and hope a lot of my next few miles are downhill !)
cheers
Paul

perhaps I should have made clear that I don't try and run it down to nothing, as others have said sludge is not your best friend
If the light does come on I fill up as soon as I can, which was easy until a couple of weeks ago, but I have commented enough about that :roll:

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Re: Panic buying, or shortage

#447964

Postby redsturgeon » October 5th, 2021, 10:18 am

Just filled up at my local Sainsburys, no queues, both petrol and diesel available. I think we are through the worst.

John

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Re: Panic buying, or shortage

#447966

Postby AWOL » October 5th, 2021, 10:21 am

pje16 wrote:
pje16 wrote:
redsturgeon wrote:It is surprising how much fuel can be still in the tank when the fuel light comes on. When I get a new car I make a point of noting this figure. With my current car, I can still travel at least 80 miles once the fuel warning light comes on.
John


Agreed John
I can do around 60 "on the yellow" before I really panic (coast, and hope a lot of my next few miles are downhill !)
cheers
Paul

perhaps I should have made clear that I don't try and run it down to nothing, as others have said sludge is not your best friend
If the light does come on I fill up as soon as I can, which was easy until a couple of weeks ago, but I have commented enough about that :roll:


The "sludge in the bottom of the tank ruining your engine if you drain the tank, so don't run your engine when the tank is nearly empty" thing is a complete myth. A lot of people were told it when they were young and it's stuck in their heads as a fact.

Let's apply common sense here, where does the fuel exit the petrol tank? From the bottom. So you are always taking fuel from the bottom of the tank no matter how full it is. Moreover, all the fuel passes through a filter just in case. Some people then say, ah but you'll clog the fuel filter if you draw the debris from the bottom of the tank. Except we already know that all fuel is drawn from the bottom of the tank so this is a myth.

Also your fuel gets mixed as you move along so any debris in the tank is going to be distributed through all the fuel.

Finally, I have kept every car I have owned for 10 years. They are almost always filled on empty. I enjoy driving with a 0-5 miles range prediction. None of them have ever suffered any damage. The best argument is that the pump could suck air and get damaged but if manufacturers wanted us to fill the tank earlier they would nudge us before we were a quarter empty as we do after all need to get to a petrol station. I've never had to replace a fuel pump so I think they have sufficient resilience to deal with ignoring these worries.

So really people should stop distributing this myth and let people relax and fear not the dreaded "sludge".

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Re: Panic buying, or shortage

#447980

Postby bungeejumper » October 5th, 2021, 10:55 am

AWOL wrote:The "sludge in the bottom of the tank ruining your engine if you drain the tank, so don't run your engine when the tank is nearly empty" thing is a complete myth. A lot of people were told it when they were young and it's stuck in their heads as a fact.

Let's apply common sense here, where does the fuel exit the petrol tank? From the bottom.

Sorry to correct, but no. The top of the exit pipe is an inch or two up from the bottom, and there's generally a sump of some sort below that where the crud can collect. Quite a lot of it is water. :) Although some of it is certainly rust. Death to high pressure fuel pumps, as my mate discovered. :( You don't want it sloshing into your exit pipe, however accidentally.

BJ

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Re: Panic buying, or shortage

#447993

Postby tjh290633 » October 5th, 2021, 11:23 am

redsturgeon wrote:It is surprising how much fuel can be still in the tank when the fuel light comes on. When I get a new car I make a point of noting this figure. With my current car, I can still travel at least 80 miles once the fuel warning light comes on.

John

I am with you there. I get an estimate by seeing how much fuel it needs to top up the tank after the light has come on. The most I have ever put in the tank is 44 litres, after about 40 miles with the light on. I averaged 48mpg on that trip, tank full to tank full, so I had some range to spare. The tank is 47 litres, having checked the handbook.

TJH
Last edited by tjh290633 on October 5th, 2021, 11:33 am, edited 1 time in total.

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Re: Panic buying, or shortage

#447995

Postby AWOL » October 5th, 2021, 11:28 am

bungeejumper wrote:
AWOL wrote:The "sludge in the bottom of the tank ruining your engine if you drain the tank, so don't run your engine when the tank is nearly empty" thing is a complete myth. A lot of people were told it when they were young and it's stuck in their heads as a fact.

Let's apply common sense here, where does the fuel exit the petrol tank? From the bottom.

Sorry to correct, but no. The top of the exit pipe is an inch or two up from the bottom, and there's generally a sump of some sort below that where the crud can collect. Quite a lot of it is water. :) Although some of it is certainly rust. Death to high pressure fuel pumps, as my mate discovered. :( You don't want it sloshing into your exit pipe, however accidentally.

BJ


Alternative views are welcome however I am not sold. The fuel isn't drawn from the top, even when the pump is in the tank it's clearly drawing from the bottom 25% otherwise the car would run out of fuel early.

Picture the fuel tank, picture the moving vehicle, how much more debris do you expect there to be during the last 25% of the tank compared to say at 50% full? I am not saying there is nothing to be filtered out, I am saying that the fuel is not drank from a pure supply that sits on top of the bottom 25%. I also cannot see how the fuel above the bottom 25% is magically debris free nor how it gets to the exit without having a similar quality as the rest of the fuel.

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Re: Panic buying, or shortage

#448001

Postby bungeejumper » October 5th, 2021, 11:41 am

AWOL wrote:Alternative views are welcome however I am not sold. The fuel isn't drawn from the top, even when the pump is in the tank it's clearly drawing from the bottom 25% otherwise the car would run out of fuel early.

Picture the fuel tank, picture the moving vehicle, how much more debris do you expect there to be during the last 25% of the tank compared to say at 50% full?

Fair enough as far as it goes, but who said the mucky bit was the bottom 25% of the tank? Not me, that's for sure. :)

A couple of inches at the bottom is deep enough to contain any crap. So set your outlet pipe anywhere above that, and all will be fine. Sure, small amounts of rust and stuff will still get stirred up, but your fuel line filter will deal with that. Until the day when it suddenly doesn't. :| Looks like you've been fortunate so far, anyway. Personally, I prefer not to invite the possibility.

BJ

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Re: Panic buying, or shortage

#448004

Postby swill453 » October 5th, 2021, 11:46 am

bungeejumper wrote:
AWOL wrote:Alternative views are welcome however I am not sold. The fuel isn't drawn from the top, even when the pump is in the tank it's clearly drawing from the bottom 25% otherwise the car would run out of fuel early.

Picture the fuel tank, picture the moving vehicle, how much more debris do you expect there to be during the last 25% of the tank compared to say at 50% full?

Fair enough as far as it goes, but who said the mucky bit was the bottom 25% of the tank? Not me, that's for sure. :)

A couple of inches at the bottom is deep enough to contain any crap. So set your outlet pipe anywhere above that, and all will be fine. Sure, small amounts of rust and stuff will still get stirred up, but your fuel line filter will deal with that. Until the day when it suddenly doesn't. :| Looks like you've been fortunate so far, anyway. Personally, I prefer not to invite the possibility.

But if the crud is below the outlet, not mixing with the fuel, then it'll never get to the outlet. It can't get sloshed up when the tank is empty, you'd already be out of fuel and broken down as air is far more likely to get to the outlet.

Scott.

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Re: Panic buying, or shortage

#448011

Postby AWOL » October 5th, 2021, 12:03 pm

what stops it sloshing up like in a snow dome?

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Re: Panic buying, or shortage

#448015

Postby bungeejumper » October 5th, 2021, 12:19 pm

AWOL wrote:what stops it sloshing up like in a snow dome?

Nothing, as far as rust and dirt are concerned. Not that very much of it will make it more than a couple of inches upward - although the deeper the fuel level in the tank, the less of it will be jolted into suspension. Either way, the vast majority of it will stay at the bottom.

With the possible exception of the Paris-Dakar rally, I think we can take it as read that all the water in the tank will stay gravitationally inclined. ;)

BJ

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Re: Panic buying, or shortage

#448059

Postby AWOL » October 5th, 2021, 3:10 pm

bungeejumper wrote:
AWOL wrote:what stops it sloshing up like in a snow dome?

Nothing, as far as rust and dirt are concerned. Not that very much of it will make it more than a couple of inches upward - although the deeper the fuel level in the tank, the less of it will be jolted into suspension. Either way, the vast majority of it will stay at the bottom.

With the possible exception of the Paris-Dakar rally, I think we can take it as read that all the water in the tank will stay gravitationally inclined. ;)

BJ


I remain unconvinced given the position of the fuel outlet in the tanks that I have looked at that there would be a sufficient difference in the amount of debris in fuel in a low fuel indicator state versus fuel indicator light off. Perhaps I am wrong but if this was a major issue then manufacturers would have made the system more robust. The reality is that they expect many drivers not to top up until the light comes on. The widely given advice of keep your tank above 25% as you don't want to damage the engine with debris just seams ridiculous. I know that any one individual only owns a few cars when they are kept until 10 year old but the fact that I have never suffered any issues from my refill a day or two after the light comes on policy makes me highly sceptical. I respect that you disagree and may even be right but I am struggling to reconcile these things.

Clearly if water was contaminating the fuel in practice I would expect to have observable issues but clearly the mitigations are effective.

The RAC says:

When an engine draws in the gunk and debris sitting at the bottom of the tank you risk damage to your fuel tank, fuel pump and filter system. As unwanted materials travel through your pump, particles can get stuck and clog the system, eventually corroding it. Repeatedly running your tank dry could also cause your pump to overheat, wearing it out prematurely.


Given some manufacturers set the alert at 10% in some cases there must be a fair amount of leeway before they are concerned about this doomsday scenario but also given that they say petrol cars can actually completely drain the tank then that suggests the fuel inlet is commonly low enough to draw from the bottom in regular use anyway.

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Re: Panic buying, or shortage

#448078

Postby DrFfybes » October 5th, 2021, 3:46 pm

FWIW I removed the fuel tank from our Carina 2 years ago.

I tipped it up and drained it from the filler, and the last bit I tipped into a plastic jug, giving the tank a good shake. Much to my surprise it came out clean.

I removed the fuel outlet and level gauge with the intention of cleaning the tank out and applying a protective coating to the inside, and as there was no rust I didn't bother.

OTOH I have found 1970s motorcycle tanks rust from te inside out at the bottom seam.

Paul

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Re: Panic buying, or shortage

#448102

Postby xeny » October 5th, 2021, 4:32 pm

Motorcycle filler caps tend to be more exposed than those on cars, so there's a greater likelihood of water getting in.

I suspect the tanks also see a greater temperature range, so more "breathing" which means more turn over of the air in the tank, so more scope for condensation.

Finally the seams at the bottom are going to be where the water collects, especially the left hand one if the bike is parked on the side stand.

Lots of factors combined.

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Re: Panic buying, or shortage

#448108

Postby pje16 » October 5th, 2021, 4:49 pm

xeny wrote:Motorcycle filler caps tend to be more exposed than those on cars, so there's a greater likelihood of water getting in.

Back in the 80s when petrol rationing was on, there was a lot of petrol theft going on (pipe and suck) when most cars just had twist on/off exposed filler caps :roll:

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Re: Panic buying, or shortage

#448115

Postby xeny » October 5th, 2021, 5:03 pm

pje16 wrote:
xeny wrote:Motorcycle filler caps tend to be more exposed than those on cars, so there's a greater likelihood of water getting in.

Back in the 80s when petrol rationing was on, there was a lot of petrol theft going on (pipe and suck) when most cars just had twist on/off exposed filler caps :roll:


The two 80s cars I know best, the Golf Mk 2 and the Metro both had filler caps tucked under flaps on the sides of the car, so reasonably protected from the weather. FWIW, the examples I worked on had locking caps, but I don't see a lock impacting water penetration.

All the 80s motorcycles I know well, Meriden Bonneville, CB100N, GSX 400, GSX 600 CBR 600, R series BMWs all had the filler cap right on the top of the tank waiting for any precipitation.

When was petrol rationed in the 1980s in the UK ?

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Re: Panic buying, or shortage

#448117

Postby bungeejumper » October 5th, 2021, 5:06 pm

xeny wrote:Motorcycle filler caps tend to be more exposed than those on cars, so there's a greater likelihood of water getting in.

I suspect the tanks also see a greater temperature range, so more "breathing" which means more turn over of the air in the tank, so more scope for condensation.

One of the interesting things I turned up recently is that E10 petrol typically contains 0.5% water. Which doesn't sound like very much, until you reflect that two 50 litre fill-ups are going to introduce half a litre of the stuff into your life. :| Under normal circumstances, your fuel injectors should be able to cope with that much, as long as it doesn't arrive all at once. But a cupful being sucked up all at once could really do quite a lot of damage to your top end.

Another slightly alarming factoid from the US media is that a goodly proportion of the grot in your tank was supplied free, gratis and for nothing, by the forecourt tanks, and by the tanker that delivered your fuel. Word is that petrol (and especially diesel) is rather adept at cultivating a particular sort of sticky slime which is capable of clogging your filters. There isn't very much you can do about that, of course. But it's interesting that some car manufacturers specify a fuel filter change every two years, while others let the job run on for 70 or even 100K. Hmmmm. ;)

Enough. I've scared myself now! :shock:

BJ


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