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Discussion Starter · #1 ·
Hi all,

Just a question. I have been getting consistently about 750Km and that will usually take me close to 0 (zero) on the remaining range indicator. When I go fill up, I only fill up about 35L which means I should still have around 10L (45L tank) left which should allow me to do around 200km (based on average 4.8L/100km usage) past the 0 mark on the trip computer.

Has anyone tried driving past the 0 mark on the trip computer range indicator?
 

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When I was a lad, I was told it was good road craft to always drive "on the top of your tank" - in other words you should make it your practice to fill up when the tank is half empty. That way you minimise picking up any water or sediment in the bottom of the tank or running out of petrol. Might apply more in Australia, where out in the bush you can sometimes travel long distances between petrol outlets. But filling up a bit early doesn't do any harm. Modern cars often do not take so kindly to running out of petrol. There's more to it these days than taking off the air cleaner and pouring half a gallon into the carburettor.
 

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Discussion Starter · #3 ·
Hmm I guess there is no harm in filling up half empty. I'm not sure about the sediment at the bottom though. I would've thought the fuel intake is at the bottom of the tank, otherwise, wouldnt there be always that couple of liters that will never be used?
 

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The fuel intake is at the bottom of the tank. Hence the concern.
 

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Discussion Starter · #5 ·
my interpretation is that the sediments will always be at the bottom. If the fuel intake is at the bottom then it will always take in the sediments as it sinks to the bottom of the tank rather than only when the tank is low/empty. ie: regardless of the level in the tank, the fuel intake will always take in fuel+sediment at the bottom.
 

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Yes, it's been done (someone one here), though I find it risky and you could damage your car. I think he drove an extra 100 +/- miles after the 0 miles remaining was on the computer.
 

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Running the petrol in the tank low - shouldn't be an issue. I think the sediment that everyone talks about is an issue for old cars and old petrol pumps. Saying that though, I've never had chance to look inside a petrol tank. If anyone knows people who has switched a petrol tank or otherwise seen one come off a car, ask 'em what the condition of the tank was.

Modern fuel injection usually works off a ring main instead of being 1 pipe feeding a carburettor, so the petrol is always being sent around that circle to be drawn off by the injectors as required. Sediment shouldn't have a chance to accumulate before being trapped in a filter or burned up in the engine. I once had bad fuel in my Belmont which gave a few 75-50-75 mph moments on the motorway when I think the injectors blocked but that sorted itself out in 1 trip.

Running out of petrol - bad news because of that ring main. Pumps are designed to work against a bit of resistance, no fuel means no resistance means that pump can go overspeed. (Extreme example - the Kursk allegedly went down because a torpedo started up in the sub, with no resistance from water to keep it at a safe speed)

I've gone maybe 30 miles past the petrol light point so far in my CT. I once got 54.32 litres in a Rover 420 that had a 55 litre tank. The actual problem point varies depending on the car. The Rover had no issues then (it had some major engine issues but the fuel system was always ok)

I'd not want to get within 0.68 litres of an empty tank again, even with the hybrid battery to give me maybe another mile :). An easy life filling up early is better than a long trek to a gas station with a petrol can :D
 

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my interpretation is that the sediments will always be at the bottom. If the fuel intake is at the bottom then it will always take in the sediments as it sinks to the bottom of the tank rather than only when the tank is low/empty. ie: regardless of the level in the tank, the fuel intake will always take in fuel+sediment at the bottom.
I think what happens is that when the tank is relatively full, the suction 'stream' created by the pump inside the tank draws upon a resivour of fuel that is several inches high. A greater volume of fuel (compared to a near empty tank) and said stream is drawing from a greater area of fuel and is defused by this volume of fuel.

However, when there is just an inch or so of fuel, the suction stream created by the pump is passing through a narrow 'channel' of fuel and the turbulence this creates (like a river) picks up debris, or anything settled on the bottom of the tank and carries it to the suction inlet of the pump (or outlet of the fuel tank).
 

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Are you doing mostly highway driving? I'm only getting 6.8l per 100km. Currently I am mostly doing city driving...but I was hoping to be more I. The range of at least 5.8. Thoughts?
 

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In the summer, I'm getting the exact same situation as the original thread starter. ITS AWESOME!!!!
 
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