Running on empty - what does it really mean?

Yes - OK, I agree that I have totally butchered the well known words to that famous song that was penned by Jackson Brown. But, if I persevere with these lyrics, here's my question:- just how much “Looking out at the road rushing under my wheels” can I do when the fuel gauge says zero?

I’m aware that when the fuel gauge goes into the “Red-zone” (i.e. the last sector on the dial), I’m using what the manual calls "the reserve quantity”. However I assume that even at zero reading, some fuel is still present in the tank -but how much and how far will this take me?

Has anyone been daring enough to find the answer to this question, or has anyone been forced into a situation where the car has physically conked-out due to lack of fuel in the tank? If so, how far did you get after the zero reading?

The other thing about which I'm not sure is what damage (if any) is inflicted on a mk7 Golf if the driver actually runs the engine dry (presumably, because the next petrol station was too far away)? Is this a no-no with the type of engines that are used in the Golf - or is it OK? For instance-is the lack of lubrication a problem for the injectors when no fuel is being squirted and the injectors are pumping?

Your views would be welcomed

Like the judge in "And Justice for All" I like occasionally seeing how much further I can go on a tank so every year or so I conk out of petrol.

Have never struck a problem after fuelling back up (Golf Mark V).

excellent aussie classic too 'Running on Empty' :)

From memory the low fuel light comes on when there is ~8 liters remaining in the tank. When the needle is pegged at empty (can't go down any further) you have ~4 liters remaining. What I don't know is how well the fuel system can physically access the last drop of fuel.

My theory is the amount left when the fuel light comes on is proportional to the distance you can drive with a full tank before the needle moves off of full.

dp

On a recent drive from Sydney to south-east Melbourne on one tank I filled up at the destination with the distance to empty saying 80km and the needle in the first part of the red sector (the thinner red part). I was alarmed that the car took 52.5 litres!

In the mk6 jetta I have the tank is rated at 55 litres. 0 km range projection equates to about 50 litres. I suspect the red zone in mine starts when there are about 7 to 8 litres left as it seems to burn through that region faster than the rest of the gauge. Lines up with that another poster above said about the red zone.

I have driven an extra 40 km after the gauge was empty and my projected range was saying 0 km. people have said that the fuel pump will be damaged but after 2.5 years I haven't had any issues. When I refilled that time it took 53.1 litres. Meaning my fuel tank had 1.9 litres approximately and the car was still running. Good knowledge to have imo but if you are in this zone I wouldn't recommend speeding for obvious reasons. If you are doing highway trips then set the cruise control to something reasonable and monitor the real time consumption. Hope this helps.

Kramer test drives car on Seinfeld - YouTube

Try this!!!!! Lol.

I have run into the red a number of times on mine now and find the warning light comes on as it reaches the red where it takes 48L. At halfway through the red it takes 50L and the few times that has happened the range was showing 60km - 80km. I did see somewhere else on this or another forum someone (in WA I think) who claims to have been able to fit in more than 57L in their mk7 which is remarkable for a nominally claimed 50L tank.

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Originally Posted by grtuned

Kramer test drives car on Seinfeld - YouTube

Try this!!!!! Lol.

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Grtuned; Kramer sure is one sick puppy! Great video and so apt to the theme of this thread.

At such a low fuel level, I'd be worried about having fuel surge and starvation issues when you're cornering, and also the other foreign deposits that you'll inevitably be putting into the tank every time you fill up.

The user manual tells you how much fuel is in the tank when the low fuel warning light comes on

Running completely out of fuel carries some risk of killing the high pressure fuel pump which will cost $800+ to replace

How would it damage the fuel pump? If it's not pumping petrol it would be pumping air which wouldn't do any harm.

It wouldn't pick up any debris in the tank because there's a filter to stop that stuff going into the pump.

The presence of unburned fuel in the exhaust system, due to intermittent or inconsistent fuel supply, may cause damage to the catalytic converter.

For direct injection engines, a lack of fuel supply may cause damage to the high pressure fuel pump, because fuel acts as a coolant and a lubricant.

Do not continually crank the engine if the vehicle is out of fuel.

The thing to remember is that the fuel gauge is really a very approximate indicator. The amount of fuel indicated will vary from vehicle to vehicle.

If you really want to know how much is there, you need to get the system calibrated. There really is not that much demand for a super accurate gauge.

Now if you want to know when you need something more than just an indicator, think of someone with an original Mini that had just a 20 litre fuel tank!

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Originally Posted by sports racer

How would it damage the fuel pump? If it's not pumping petrol it would be pumping air which wouldn't do any harm.

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Well explained by Diesel_vert

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Originally Posted by Diesel_vert

The presence of unburned fuel in the exhaust system, due to intermittent or inconsistent fuel supply, may cause damage to the catalytic converter.

For direct injection engines, a lack of fuel supply may cause damage to the high pressure fuel pump, because fuel acts as a coolant and a lubricant.

Do not continually crank the engine if the vehicle is out of fuel.

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The following may help explain why the high pressure fuel pump needs fuel for lubrication and cooling

Normal fuel injection into the inlet manifold only uses 40~60 psi fuel pressure

The direct or stratified injection systems (into the combustion chamber) run fuel pressures up to 2200 psi on some vechicles (1,900 PSI on the FSI engines)
(The fuel rail is often thick walled to ensure it's strong enough to hold the pressure)
The internals of the high pressure fuel pump are created on a very expensive machinery and have incredibly tight and consistent internal tolerances (you could not make one on a lathe for example)
The high pressure fuel pump is not lubricated by oil
Creating ~2200 psi of pressure creates heat - fuel must be present for both lubrication and cooling

One of the tuning upgrades for the FSI engine was an upgraded high pressure fuel pump,
buying this outright costs $1,650 and even $1,200 if you exchange your stock pump
APR - High Performance Development for Audi, VW and Porsche Vehicles.
(There is no need to upgrade the TSI high pressure fuel pump)

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Originally Posted by Diesel_vert

The presence of unburned fuel in the exhaust system, due to intermittent or inconsistent fuel supply, may cause damage to the catalytic converter.

For direct injection engines, a lack of fuel supply may cause damage to the high pressure fuel pump, because fuel acts as a coolant and a lubricant.

Do not continually crank the engine if the vehicle is out of fuel.

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I'm trying to understand why there would be fuel in the exhaust system due to intermittent or inconsistent fuel supply. If the engine is running it should burn all the fuel that enters each piston as per usual no?

Quick reply:- No

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Originally Posted by Idle

Quick reply:- No

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Looking forward to more details.

Slightly less quick reply:

Well, for a start, petrol engines have an optimum air to gas (evaporated petrol) ratio at which they run best and give their best power to economy performance. My aging memory suggests 14.7 to 1, but anyway it's thereabouts.

Long periods below this will result in a hotter running motor — substantially below can cause valve damage and even burn holes in pistons.

Ditto above this will result in a colder engine and unburned fuel in the exhaust system and in the oil (when you see black smoke from the exhaust, petrol or diesel, this indicates unburned fuel exhausted from the motor, and will result in poor economy.)

This has been the case for as long as there have been internal combustion engines, and never more so than today, with compression ratios of petrol motors approaching those of diesels, manufacturing tolerances very fine and materials cut to the limit (and sometimes beyond...)

A quick google will bring you more detail on the subject — probably more than you can cope with.

As per above, an engine needs a stable and consistent fuel supply for combustion to occur normally.

An intermittent or inconsistent fuel supply may cause the engine to misfire, a condition where fuel is burned partially or not burned properly. This allows raw fuel to pass through the engine and into the exhaust system.

As the exhaust system in a petrol engine is normally very hot, raw fuel is ignited by the heat and causes a large temperature increase. This will cause damage to the catalytic converter, as well as other components in the exhaust system.

Almost every passenger vehicle fitted with a catalytic converter will have the same warning written in the owners manual.

https://www.youtube.com/watch?v=Vq25ZJwZJzU

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Originally Posted by gareth_oau

Video

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Gareth: would it be an exaggeration to call it "a timeless classic" ? Doesn't matter if it is - still an-oldie-but-a-goodie!

there will be many here that have never heard it before.

My job as an oldie it to educate those youngsters! LOL

Haven't been able to view the video yet but I have another question for you experienced guys. Running spark plugs past their due date. What are the serious issues with running plugs that are to be changed at 64,000km to say around 69,000km.

Also in my 1.4 tsi Jetta if I go full throttle in gear 3 and 4 after the engine has warmed up I feel the car misfiring then the EPC light comes on and the car disables that cylinder that was misfiring. Switch off the engine and restart and the EPC light clears and the car is back to 4 cylinders. Wasn't able to change the plugs till 69,000 so was wondering what potential damage may be done even though the car seems fine now.

I was talking to some friends about this recently. A few told me they like to play a game to see how far they can go before running out. I was just like "why bother? just fill up when it gets low or anytime fuel is cheap". I don't get it personally. Why run the risk of getting stranded?

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Originally Posted by Lemonskin

I was talking to some friends about this recently. A few told me they like to play a game to see how far they can go before running out. I was just like "why bother? just fill up when it gets low or anytime fuel is cheap". I don't get it personally. Why run the risk of getting stranded?

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Seems like a daft game to play in all honesty. Not good for the engine, and no real satisfaction in the end... at least for me. I'm blessed with a "range" guide, so I use that to determine how long I could've gone on a tank. I usually try and keep mine above half, or top up whenever the fuel cycle goes to the cheap price. Speaking of which, pumps are starting to go back up again, around the 155 mark.