Venting capacity – reserve warning light faith

[PermaBuzz]

How much additional fuel capacity does venting gives you?

What I mean is this. I own (well VWoA owns) a 2005 Jetta TDI sedan. I have been tracking mileage as well as distance I can travel on 1 tank (about 500 miles per tank). My concern is once the fuel warning light comes on. I understand that is supposed to happen with 1.5 to 2 gallons left (by my numbers I should be able to go 50 to 75 miles on reserve).

Well, within 15 miles of the warning light coming on I filled up, vented for a total of 14.516 gallons diesel. So I either have a warning light that is way off and I “got lucky”, or by venting I am able to use the full 14.5 gallon capacity PLUS an extra amount because of venting. My question is how much is that extra capacity?

I have done the searches here and see anything from no additional capacity to 2 or 3 gallons. So what is the safe number to use? Can you trust the warning light to be 2 gallons remaining regardless of whether you vented or not?

The numbers so far: 2005 (A4) Jetta Sedan, Automatic.

2100 Miles since new (4/12 delivery)

50/50 city/hwy driving

Hwy speeds tend to be on the higher side (75mph +/- but below 2500 rpm’s)

Averaging about 37mpg

PB

 

[tditom]

my A4 (01 Golf) can fit over 17 gallons.

I think my fuel light comes on when there are about 1.6 gallons left. This evidently varies much from car to car.
-tom

 

[Old Navy]

Most I ever put in a my vented '00 NB was 16.5 gallons after driving only about 15 miles with the warning light on. Since the B100 was foam free and B100 was what I have been runnig for several tank fulls, my best guess is about 17.5 to 18.5 gallons.

 

[mrGutWrench]

my A4 (01 Golf) can fit over 17 gallons. I think my fuel light comes on when there are about 1.6 gallons left. This evidently varies much from car to car. -tom

__. I've been less than 1/2 mile from a station when the light went on about 4 times. Each time, it took about 14.9 gallons to fill -- I'm ventectomied, filled to liquid fuel at filler neck.

__. I've driven for about 65 miles after the light went on twice. Both times, it took about 16.1 or 16.2 gallons to fill. I'm pretty sure that my light is set to illuminate a little earlier than the 1.9 gallons that VW specifies. (BTW, most people who have run dry - by accident or on purpose - have found that it takes about 17 gallons to fill all the way; that's fully vented or ventectomied.)

__. Also see Old Navy's post below. A number of people have found that fills with biodiesel results in more gallons going in the tank. Many think that that's due to less foam with bio-d but it's not been fully investigated.
'

 

[bradfa]

My one and only fillup (that I've paid for, dealer paid for first one) with my 2005 Jetta, I fit 14.1 gallons of B100 in, venting. Could see fuel in the neck. The warning light came on as I was turning into the station. It took a whole lot o' pushin that little button, time to do ventectomy I think

 

[weedeater]

16.8 gallons in the tank, some more in the neck and filter.

around 1.8 gallons is reserve. The warning light level is adjustable.

 

[DrewD]

My 5 speed 04 gets 500 miles on the first 1/2 tank and then another 250 miles before the light goes on. I didn't realize the auto took such a big hit on the fuel economy.

I typically put in 16 gallons or so when I refuel.

 

[SilverTDIPDJetta]

I can fit 2.5 - 2.6 gallons after the pump shuts off automatically. I fill it until I can see the fuel level in the filler. This gives me a little over a 17 gallon capacity.

 

[PermaBuzz]

My 5 speed 04 gets 500 miles on the first 1/2 tank and then another 250 miles before the light goes on. I didn't realize the auto took such a big hit on the fuel economy.

I typically put in 16 gallons or so when I refuel.

I'm sure my economy would improve if I spent more time on the highway... especially if I keep my right foot under control. I will be going on a longer interstate trip soon. That'll be the mpg test. Keep in mind that of those 500 miles, 250 of them were in town. The balance were on the highway.

 

[Genesis]

I can get to 500 miles at the 1/2 mark if I keep my foot out of it and drive on the highway.

I do neither, have larger nozzles, and get between 425 and 450 miles to the half mark consistently. The low fuel light typically shows up right near 700 miles. Average MPG runs in the 44-48 range, depending on the mix of driving for a particular tank. I typically stuff in the mid-15 gallon range on a fill if I tap it immediately after the light comes on. I've put in just over 16 gals, and was starting to sweat about the possibility of running out.

That's with a fill to the neck with visible fuel, vent guts are in a parts drawer in my garage.

On long trips I'm sure I'd do better but I tend to run at about 80mph which doesn't do anything good for economy

'03 Jetta Wagon, 520 nozzles, otherwise stock.

 

[meganuke]

Official VW capacity is 14.5 gallons. If you fill to the brim, that's probably another .5 gallons. Venting gives you another 2. I've filled mine with 17 gallons.

The best way to find your actual reserve capacity is to fill up as soon as the light comes on. Subtract the amount put in the tank, fully vented, from 17. That will be very close to your actual reserve.