Because I'm obsessively cautious I normally fill up when the gauge gets down to half full. However, it recently occured to me that this meant that I was never getting a full tank of fresh fuel and that a proportion of the tank's contents will now be 5 years old. What effect, if any, will the practice of filling up like this have?
(Ignore the fact that for a lot of the time I'm carrying around more weight/mass of fuel than is strictly necessary.)
Edited by L'escargot on 14/08/2008 at 22:14
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Say you do 9,000 miles a year and that your economical car does 300 mpg on a half-tank; that's 30 refills per year, or 150 over 5 years.
Each time you refill the car, half of the fuel is the old stuff, and half of that old stuff is the fuel from the refill before that. So the proportion of one-year-old fuel is 1/2^30 (or 0.00000009%), and the proportion of one-year-old-fuel 1/2^150.
In fact, only 0.003% of what's in your tank is over 6 months old, so I wouldn't worry about it.
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I guess there will still technically be some old fuel in there but it will be so dilute as to not matter.
It reminds me of a friend who, when a student many years ago, worked for a summer in the kitchens of a well known seaside holiday camp. He was charged with keeping the storage vats of boiled vegetables topped up prior to and during mealtimes. At the end of his first day he thought he would show initiative and clean out the vats. He got a row from his boss when he was found doing that on the basis that it was a waste of stock. He was instructed to simply turn them off and put more peas or whatever in them the next day.
He couldn't help thinking that it would have been possible to be served some veg in early September which had first been cooked at the end of May and had been heated up every day in between !
I hope and trust that this method has long been banned...............
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You've seen the Rogue Kitchens programme then ;-) An eye opener
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300 mpg on a half-tank; ??
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300 mpg on a half-tank; ??
oops! I meant 300 miles on a half-tank, and now it's too late to edit the post.
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I think most of us knew what you meant, NowWheels.
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I meant Rogue Restaurants. Same presenter as on othen "rogue" programmes.
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No, I haven't seen that one rtj but I am not a big fan of TV really. I take it similar horrors were portrayed ?
Guess we'd better talk about petrol again or we'll be for the high jump !
Was there one about rogue petrol stations ?
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it recently occured to me that (.) a proportion of the tank's contents will now be 5 years old. What effect if any will the practice of filling up like this have?
Effectively, none. Think about this - some part of every single thing that you will ever eat remains in your body for your whole life. It's the same for your car, and whatever you put in the fuel tank.
Edited by FotheringtonThomas on 14/08/2008 at 23:00
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If it makes ytou feel any better once per year you could go for the refuel light (if your car has one) and run the tank down.
Disclaimer: I will not be held responsible for any crud coming through and blocking your fuel filter.
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Fuel injected cars (that's all moden cars) recirculate the fuel back to the tank so it's constantly being mixed.
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" some part of every single thing that you will ever eat remains in your body for your whole life. "
Tell me about it. When I was five I was forced to eat a Brussells sprout and believe me, I can still taste the b....
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Take an occasional drive in my area and the numerous speed ramps and potholes will thoroughly mix whatever fuel is in the tank. Probably loosen a few teeth, as well.
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Live dangerously - every third fill-up run it to one quarter full. So long as you fill up very late at night, no-one will ever find out what a dare-devil you are.
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We're still breathing the same air as Julius Caesar, aren't we?
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This is what you need to read:
en.wikipedia.org/wiki/Solera
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Until recently on getting a different car I put a spare can of petrol in the back, drove it till the fuel guage read zero or the fuel warning light came on , set the trip mileometer to zero, and continued warily till it ran out, also noting how many miles from a quarter full to zero.
If you have a metal fuel tank [not many left now] it makes sense to keep it over half full - above its seams - less likely to rust from the inside that way, especially if not used very often like my 28yr old TR7 [original tank].
With plastic ones, fill to just above half full to avoid carrying excess weight around......and if passing a cheap petrol station, fill completely!
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One thing does occur to me re all of this... if you fill your tank every time when it is half full, surely you're leaving a higher percentage of any crud at the bottom than if you let it run almost dry every time.
So therefore, would it not be a better idea to let the car run on vapours every time than refill at half-full?
Every time you fill up at half-full, you're clean. But if you let it slip only once after 100,000 miles, there will be more crud at the bottom of the tank after all this time, potentially enough to break the fuel filter.
Whereas if you run on vapours every time the small amount of crud is being dealt with on each occasion. Since the fuel filter is periodically replaced, it should be able to deal with it.
Am I talking crud here?
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>>Am I talking crud here?
Yup. If you do 100,000 miles, you will put in 10,000 litres of fuel, no matter how often you fill up. Each litre of fuel contains two grains of sand, so there will be 20,000 grains of sand in the bottom of the fuel tank no matter how frequently you fill up.
On theother hand, if you want to move them from the petrol tank to the fuel filter, then move onto running on vapour!
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> On theother hand, if you want to move them from the petrol tank to the fuel filter, then move onto running on vapour!
Ah, yes. I see the flaw in the evil plan now...
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No, the flawed logic would be:
The grains of sand settle at the bottom of the tank, but only move through into the fuel line when the tank is run low. (I don't believe that is true, but the popular myth is that it is so)
Therefore if you keep filling the tank at the half way point, the grains accumulate harmlessly.
If you ever let the tank go right down, all the accumulated grains will go through at once and block the system
If you sometimes let the tank go low, the grains will be swept out in smaller concentration, so will be caught by the filter but will not cause any blockage.
So logically you need to stick to one or the other - regularly empty, or never empty.
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For this experiment you need a milk bottle, some tea leaves, and some water.
Add a pint of water and a teaspoon full of leaves to bottle A, and a quarter pint and teaspoon full to bottle B.
Allow a few hours for leaves to settle.
Pick up bottles, turn through 45 degrees on the vertical access, left right, left again.
Check which one has more sediment in suspension.
Now imagine that as full tank/empty tank scenario...
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For this experiment you need a milk bottle some tea leaves and some water. Add a pint of water and a teaspoon full of leaves to bottle A and a quarter pint and teaspoon full to bottle B. Allow a few hours for leaves to settle. Pick up bottles turn through 45 degrees on the vertical access left right left again. Check which one has more sediment in suspension.
backrooming 1970's open university tv style :-)
Edited by welshlad on 15/08/2008 at 18:02
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backrooming 1970's open university tv style :-)
Here's one I made earlier...
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What a thoroughly over-optimistic lot you all are.
The tank is not half full, it's half empty.
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