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The Royal Automobile Club (RAC) in Western Australia has warned motorists against running cars down to the bottom of the fuel tank, explaining that it can do damage to your car.

RAC WA says allowing your fuel tank to run low can cause sediment in the bottom of the tank to clog the fuel filter.

Running on empty can also cause the fuel pump to become exposed and overheat, as it is designed to sit submerged in the fuel.

Finally, the RAC WA warns you could lose control of your car if the tank runs completely dry and the brakes and power steering stop functioning.

RAC head of member advocacy, Matt Brown, said high fuel prices were pushing more and more motorists to hold off refueling their cars until well after the little red light came on.

“Our figures show that when petrol prices start going up significantly, people do start stretching it to the limit in terms of trying to get as much as possible out of their tank before having to refuel,” Mr Brown said.

“It’s a significant issue for low-income and fixed-income earners who don’t have the capacity to fill up at will.”

The RAC recommends filling your tank before it drops below one-quarter full.

It also suggests that you can save around $500 each year by filling up at the right time in the cycle.

According to the Australian Competition & Consumer Commission, Wednesday has been the cheapest day to refuel your car in Perth in recent weeks, while Thursday has been the most expensive.

In Adelaide, Thursday and Friday have been cheaper recently, with Saturday and Sunday the days to avoid.

Friday is the safest day to refuel in Melbourne at the moment, with prices tending to peak from Saturday to Monday.

Sydney and Brisbane have been similar, with prices lowest on Thursday and Friday and hottest around the weekend.

Do you have any tips on finding cheap fuel in your area? Let us know in the comments section below.

  • Carl

    What a load of bull. The whole purpose of having a fuel filter is to catch any sediment. If a fuel filter is not changed at the specified time/mileage, then that’s a whole separate issue. I always run my tank right to the bottom and have never had any issues at all.

    • jess

      wow your lucky that you’ve managed to time it so well to run out of fuel “right to the bottom” just you pull into the pump

      • D

        The pickup is actually on the bottom of the tank? Its a myth.. And u loose brakes and power steering when engine vaccum is lost ( but u get apron three pumps after engine vaccum Loss because of the check valve but each press weaker till no booster assistance.

    • Hung Low

      The sediment still has to past through the fuel pump first pre filter. If anything you will prolong fuel pump life by not running low on fuel!

      • Trump

        Who can see the conflict here. By not running your tank empty, RAC roadside assistance doesn’t have to respond.

        • Vlad

          another thing…. when one runs the fuel all the way down, there is sediment-building old fuel in the tank. No sediment, no problem.

    • TheRainKing1978

      You point makes sense to me regarding the sediment but a fuel filter running dry is bad like any fluid pump they are designed to be submerged otherwise they run hot which either shortens the life or potentially ends it depending on other variables. I ran it low like this myself often until I burnt up a fuel pump. I’d rather not drop a gas tank to replace a fuel pump if I can avoid it by fueling up more often.

  • CS

    What a startling and groundbreaking relevation this is. Maybe they could put a patent on this theory and sell the idea worldwide, or perhaps they should just realise that ever since cars have had petrol tanks, sediment will collect in them at some stage – hence a filter. What is the next thing RAC will tell us – If there is not enough air in your tyres then they may be slightly flat, especially on the bottom.

    • Biker

      Ah, but when the bottom is flat the top still OK? And you can try move air from the top to the bottom by rotating the wheel 😉

      I will patent this idea first thing in the morning and I shall call it i-Diot.

      And I would love to make use of the fuel cycles, as soon as I figure out how they work and when the bottom of the cycle occurs. This I will call i-nformative 😉

      • CS

        I like your ingenuity….you have my support with the tyre invention …..by rotating the flat spot to the top you no longer have a flat tyre…my thinking is that if you filled up you tyres with something lighter than air – say helium – the flat spot would always be on the top. The tyre would contain air at the bottom, helium in the middle and nothing at the top, so where the nothing is which is now the top, that would be the flat part, and seeing as you drive on the bottom part you wouldnt notice that its flat. You can borrow my idea – maybe patent this as well and call it i-Diot 2.0…

  • Robert

    …and they just tell me this NOW!!! After driving and owning cars for over 15 years!!! WOW!!!!!

  • QAZ

    “RAC WA says allowing your fuel tank to run low can cause sediment in the bottom of the tank to clog the fuel filter.”

    I would think that while you drive, you are “shaking the tank”, mixing whatever it is inside the tank. It doesnt really matter how full the tank is?

  • QAZ

    It is risky to leave filling up last minute however. Occasionally you may just run out of oil when the price is at the highest.

    Just fill up when the price is good I reckon.

    • Beav

      ^^Why would you run out of oil because your gas was low?

  • john

    Doesn’t the sediment slop around in the tank with the fuel. How can it not move at all ?

  • Jack

    I have always been told this.. And it is true..

  • charlie

    I always thought that Regardless of how much fuel is in the car the pick up point for the fuel does not change.

  • Hubby

    The way my wife drives, there is now way in the world that any sediment could ever settle enough to cause any long term problem – in fact, the way my wife drives, cars are only a short term kind of thing..

    • scatman

      Is she so fat the car tilts to one side?

  • Vibe

    But playing petrol station roulette is fun!

  • Antman

    But doesnt the pump suck fuel from the bottom of the tank anyway? Where the sediment is…!!!

  • Acfsambo

    One thing I have been told (though not sure if it is true) is that some modern fuel pumps, especially higher volume ones pump more fuel through them then they need and dump the fuel that doesn’t make it into the system back into the tank. I was told it does this to stop it from overheating (like a coolant).

  • Smitz

    Must be kidding with that white car on the photo! That is a LADA 2107 (apparently rotten at the bottom) – a very primitive car based on the FIAT 124 Saloon (European car of the year 1966 award) and is _still_on_production_ in an almost unmodified way. It’s fuel pump is located under the hood and in the majority of cars it is mechanical because most of them are carburettor based. It has no power steering so that is not a problem either. It’s brakes are rubbish no matter if engine is running or not. Definitely a wrong car for the article.

    • Golfschwein

      hehe, you beat me to it. A Lada. Is that the best photo anyone in the world could find of a bloke filling up a fuel tank? It’s a great juxtaposition to the next photo of an ultra-modern Jap instrument display.

  • Flying High

    But you use more fuel when the tank is full. And performance is also affected. At 60 litres, you are carrying about 42kg of weight just to fuel the car. Of course there are a number of car journalists who could afford to lose about 42kg of weight themselves, but that is another story…

  • laurie

    My fuel gauge has a mind of its own! it shows full longer than its indicating then the so called linear gauge starts loosing level at a faster rate towards the bottom of the tank I was under the impression that car manufactures left about 20L when the gauge showed empty or near enough to empty!

    • Sam 300TD

      I thought the rule was 10 litres left from when the light cam on…

  • Y

    Seems pretty obvious to me that real intention of the article is to reduce callouts RAC makes to its roadside assist members for empty tanks. Reducing the callout load by 5% would probably get some RAC bean counter a promotion.

    No doubt it will be effective, despite there being no factual basis to the claim. Most people are strongly motivated to reduce “damage” to their car engines .

  • Sam 300TD

    My fuel gauge doesn’t move of full for the first 120 or so k’s. Maybe I should fill it up at this point because it has hardly used any. The last half of the tank disappears in 200k! :)
    Plus the cycle thing is a load of rubbish. Diesel has been stuck on 155.9 here in Cairns for a few months now. It can cycle back to 1.20 any time it likes.

    • PB

      Of course it’s true,
      Ever changed an in tank pump due to a burn out?
      The sediment usually ends up as a ‘mud’ in the very bottom of the tank but smaller solid particles will still float at a higher level. The manufactuers these day put the fuel filter as a close weave metal screen on the inlet of the pump. An EFI pump operates at high pressures and therefore sucks a fair amount of debris into the filter, which is a pain in the butt to change as it is in the tank.(something to be said for external filters and pumps)
      The in-tank pumps do need to be immersed in fuel for cooling, they are designed this way. Even an external pump will run very hot but they are designed for it.

      Simple really, just keep your tank above a quarter you have less chance of clogging the pre filter and overheating the pump. EFI pumps are not cheap either…

      Good advice from the RAC but something most people seem to be well aware of anyway. Cheap way to prevent unecessary repairs really.

      Just my two cents worth…

  • Shak

    I’ve dont this loads over the years, and have seen that with most of my cars, there is at least 10 litres left in the tank anyway when the light comes on, so even if it is true, my filter, and pump would not be in any real danger. Only IF it were true, but thankfully it isnt.

  • Servoman

    Look, fuel is taken from the bottom of the tank – always – and that is where the sediment lies – once again – always. I dont know what they are on about – you cant take fuel from the top of the tank where there is no sediment, because you would run out of fuel after about 5 minutes of driving, and still have a full tank – unless the fuel pickup line floated on the surface which it doesnt. And as Y stated – it probably has more to do with reducing the RAC callouts than anything else.

  • Bob_Troopy

    The fuel may slop around more when the fuel is low in the tank “possibly” washing more sediment from the bottom of the tank and into suspension. But if the car has been driven at the normal average rate of about 20K per year then the sediment will be pretty stable in that any fine stuff will already be in suspension most of the time, and on the bottom will be larger bits that will stay there unless you get some really crazy driving attitudes with a low tank. These will be filtered out by any fuel filter anyway. So basically I reckon.. yeah a load of cods wallop. This is similar to the other b/s theory of a dirty filter will let more crap into your fuel pump. No it won’t, it will only restrict fuel flow and may starve your pump.

  • RACV_Mechanic

    My two cents worth.
    Be careful not to buy a car with the petrol pick-up located at the driver’s side of the tank. The petrol pick-up should be on the passenger side of the tank, that is the left side of the car. Aussie road cambers can be up to 10%. This means that a car with a drivers’ side pick-up, parked on the left, on a road with a camber, may well be clear of the top of the petrol. In the morning your car may not start even if your tank is a quarter full.
    If your car is designed for Australian conditions then the pick-up must be on the passenger side.
    If your car has the pick-up on the drivers’ side then it is advisable to carry an extra 10 litre container of fuel. Or you can jack up the left side of the car, let the jack off quickly before the car runs out of fuel and drive onto level ground.