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TDI Fuel Economy Discussions about increasing the fuel economy of your TDI engine. Non TDI related postings will be moved or removed.

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Old November 11th, 2005, 10:27   #1
TDIgnifyd
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Default How much fuel left after LOW FUEL LIGHT comes on?

OK - how much more kms/miles do guys drive after the low fuel indicater light pops on? I would especially like to hear how far PD-TDI go.

The manual states there is approx. 7L in the reserve tank - is it safe to assume that this reserve is hit at the moment the light comes on?

The furthest I've gone on a single tank is 753 km so far, and I'm quite anxious to see when exactly the great MPG starts to kick ... i know, i know, be patient and all... seing that I just have over 2,000 KM (1500 miles) on the dial.
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Old November 11th, 2005, 10:59   #2
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Default Re: How much fuel left after LOW FUEL LIGHT comes

http://forums.tdiclub.com/search.php?Cat=0
Covered in depth.
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Old November 11th, 2005, 15:18   #3
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Default How much fuel left after LOW FUEL LIGHT comes on?

7 Litres, 1.9 gal; sounds about right. However, everyone agrees that when the light comes on varys from car to car, so be careful.
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Old November 11th, 2005, 15:34   #4
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Default How much fuel left after LOW FUEL LIGHT comes on?

Quote:
OK - how much more kms/miles do guys drive after the low fuel indicater light pops on? I would especially like to hear how far PD-TDI go.

The manual states there is approx. 7L in the reserve tank - is it safe to assume that this reserve is hit at the moment the light comes on?

The furthest I've gone on a single tank is 753 km so far, and I'm quite anxious to see when exactly the great MPG starts to kick ... i know, i know, be patient and all... seing that I just have over 2,000 KM (1500 miles) on the dial.
You will be getting an extra 150-200 km's if you "vent" while fueling. You will encounter 7-7.5 liters/100 km for now but it will go down to 6-6.5 after a few thousand km's. You will notice a power increase and fuel consumption decrease at around 10K km's. Took 30K Km's for my Golf to get to where it is now(Which is 4.68 on the highway @ 120 km/h and 5.2 city driving. The car has 44K km's now and fuel consumption has been that way since 30K km's.).
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Old November 11th, 2005, 15:59   #5
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Default How much fuel left after LOW FUEL LIGHT comes on?

Quote:
how much more miles do guys drive after the low fuel indicater light pops on?
About a week of commuting.
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Old November 11th, 2005, 21:17   #6
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Default How much fuel left after LOW FUEL LIGHT comes on?

Quote:
Quote:
how much more miles do guys drive after the low fuel indicater light pops on?
About a week of commuting.
I think that your commute may actually be shorter than mine, Nick. Of course with my driving habit, I'm not really able to go that many more days.

Edit:

For the OPie, I usually hit the warning light either on the way to work, or on the way from work. If I'm on the way to work, I get fuel on the way home, and if it's on the way from work, I get fuel on the way home.

But a few weeks ago, I was out driving around with no particular place to go and saw that I was getting low and I started wondering where I would be when the light came on. Well, after some general calculations, I wasn't sure. I knew that I have enoguh after the light to get to my regular fuel stop, so I wasn't worried.

Well, I was driving along and decided to try a road that I had never been on before. It took me out of the way a little bit.

Then I hit a town where I saw an FJ-40 for sale, so I circled around and took a look at it, then I decided to take the back way to town but missed the right turn and ended up taking a longer route home.

So there I was. I just turned off of the Parkway and went through the lieght (it was green) and I was within an eighth of a mile of my fuel station and the light came on.

How weird is that?

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Old November 11th, 2005, 22:13   #7
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Default How much fuel left after LOW FUEL LIGHT comes on?

Well, I've calculated out for each tank, based on a 17.0 gallon capacity, miles at chime, miles at fillup, gallons filled, and tank MPG. The equation is below

((17-(Gallons Filled-((Miles @ Fill - Miles @ Chime)/Tank MPG))) * Tank MPG) = Miles To Empty @ Chime

The number of miles to empty goes up as the miles at the chime go up (due to increased MPG), but even on my tanks where the mileage was in the upper 40's there was a minimum of 114.7 miles to empty when the light came on at 690 miles and the tank returned 47.3 MPG. My highest is 166.97 miles when the light came on at 840 miles and the tank returned a 59.2 MPG.

I should have gotten more on my 61.1 MPG tank, but...

I drove to work (17 miles) and arrived with 1001 miles on the trip odometer - no problems. Based on my above calculations I should have been to make it to 1050 miles at least (was hoping for 1100 maybe ). The car sits for ~8 hours, and go and start it up, but all it does is crank over. After ~10 seconds of cranking it fired up an idled ok. I drive off and notice that it has very little power, almost shuts off when I let up on the throttle to shift, minor stumbling, etc. It finally dies ~ 1 mile from work. I put in a measured 0.75 gallons of fuel, get it restarted, reset my trip odometer and drive to the gas station. I fill up the tank as usual (vented clear to the top) and then put an additional 0.75 gallons in my spare container for a grand total of 16.38 gallons . I was assuming I would be much closer to 17 gallons. All fuel volume measurements taken from the same station, same pump, same nozzle facing the same direction and on the same day.

What I'm wondering/suspecting, that the injection pump transfer pump lost it's prime while setting for the day (I've had previoius air entrainment problems that were never resolved - long story), but had enough fuel to get me a mile before it wouldn't run any more. If I had not let the car set for the day, I would have probably been able to use more of the fuel in the tank. I have a hard time believing that my particular fuel tank is 0.6 gallons smaller than what others have posted, but maybe.

Guess I've drifted a bit off topic here, but still kind of applies. Any thoughts?
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Old November 14th, 2005, 06:58   #8
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Hmm... interesting. Seeing that I've yet to vent my tank (I really shoud, to start testing my fuel economy calculations) ... most of my fillups have been consistently between the 48-49 litre ranges (as far as the display on the pump is concerned) ...
So, effectively I should be able to achieve at leas 6.5L/100 for the reserve ... is that really much you guys drive after the light comes on? Kinda risky ain't it?
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Old November 14th, 2005, 11:47   #9
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I've gotten as much as 92 miles after the light came on. I was really pushing it. To me, how far you can go after the light has come on is a function of your mpg for the last 1.9 gallons.

To me, it doesn't matter if you vent the tank. When the light comes on, it is measuring what is left in the tank, not what you started out with. To be conservative and know how far you can go just figure your average mpg and multiply that by 1.9 gallons. If you want to push it, estimate your best mpg and multiply.
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Old November 14th, 2005, 17:49   #10
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for a jetta and golf a4 version, when the light comes on book says 1.8 gallons
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Old November 15th, 2005, 06:33   #11
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my max fill has been 17.05 gal, well over 100 miles after the warning. I've filled over 17 gallons twice
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Old November 15th, 2005, 10:07   #12
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I usually dont take it past 40 miles once the light kicks on. It's really hard on the fuel pump/injector pump when you run out of fuel.
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Old November 15th, 2005, 11:38   #13
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Quote:
Originally Posted by rez311
I usually dont take it past 40 miles once the light kicks on. It's really hard on the fuel pump/injector pump when you run out of fuel.
You are not going to run out at 40miles after the light comes on. Trust me.
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Old November 15th, 2005, 12:16   #14
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Quote:
Originally Posted by jokila
You are not going to run out at 40miles after the light comes on. Trust me.
So do you consistently drive after the light comes on then fill say, after you've driven 75-90 miles?
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Old November 15th, 2005, 19:31   #15
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On my 871 mile tank in October, my light went on at 792 miles, so I went 79 miles after the light came on. My average tank mpg was 53.5, and I filled up with 16.29 gallons. So this either means I averaged 66 mpg for the 1.19 gallons that I used before filling up, or that the light came on at about 2.2 gallons (assuming I drove 53.5 mpg consistently). I'm not sure which is more realistic - probably something in between these two scenarios. I hope that the light tends to trigger on the conservative side, meaning 1.9 gal is the published value, but it always turns on somewhat above this amount. (I'm assuming my tank holds 17.000 gallons unless I fill more than this amount some day.)
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