Fuel tank size (F11)

[Jobbo]

I've only had my F11 for 5 weeks but I've filled it up five times already. The handbook says the tank is approximately 70 litres, which would be great; however, I have yet to get anything more than 64l into it. Last night the range was down to 14 miles and the permanent warning of miles to empty had been on since 30 miles remaining, but there should still be ~6l to use.

6l at 23mpg (worst case) would get me over 30 miles so the range reading seems very pessimistic. I'm not sure I'm willing to see how far after 0 miles it will run, though. Has anyone taken the gamble and managed to fit anything near 70l into their F10/F11? I'm guessing the fuel tanks are pretty much identical for petrol and diesel models.

[Wills2]

The gauge under reads due to the fact that running the tank close to dry can damage the engine.

[Jobbo]

I regularly put 64l in my 66l Merc C-class fuel tank though. If the tank needs to retain over a gallon when reading 0 miles to empty, they shouldn't state a capacity of 70l.

[Wills2]

But that is the capacity of the fuel tank, 70 litres.

BMW feel that running it dry or close to dry could damage the engine and impair performance so they under read on the gauge.

I fill up on a 1/4 as I don't like running cars on fumes, but you could test the theory.

[Helicopter123]

Why would you want to run the car on fumes anyway?

[Jobbo]

A gallon and a half of petrol is not fumes. Why would you not want to use the full range of your car?

[Higgs boson]

Wills2 said:

The gauge under reads due to the fact that running the tank close to dry can damage the engine.

Please explain.

[hornetrider]

My E61 is also a 70l tank. I too, am a fuel nazi and don't like filling up too early, hence I run it very low. When the range gets down to zero and I've filled up I've never got more than 66l in it, ergo I have ascertained that there is a ~1 gallon 'reserve'.

So, I won't have any qualms running it 15/20 miles from when the range hits zero.

[Wills2]

Higgs boson said:

Wills2 said:

The gauge under reads due to the fact that running the tank close to dry can damage the engine.

Please explain.

That's what the manual says hence my explanation as to why the fuel gauge is under reading all my BMWs have under read.

"If the fuel range drops below 50km, 30 miles, you should refuel as soon as possible, or engine function may be impaired and damage may occur."

I presume the fuel system, lines/pumps/injectors etc...are designed to work with fuel running through them?

[Jobbo]

It is potentially damaging to the fuel system of a diesel to run it dry, but it's not an issue on petrol cars.

Very tempted to take a 1-gallon petrol can with me at some point and run it to about 30 miles past zero.

[Wills2]

That's from the manual of my petrol 5 series.

I bet you can do 30 miles more though.

Edited by Wills2 on Thursday 26th March 15:08

[drmark]

I struggle to see why you think the fact that the fuel gauge / range is overly pessimistic by a few litres / 16 miles warrants a second thought, let alone a post on a forum. Seems a perfectly sensible margin of error on a 75litre tank / 4-600 mile range (depending on your car).
But each to their own

[andyeds1234]

Jobbo said:

A gallon and a half of petrol is not fumes. Why would you not want to use the full range of your car?

Tell you what, why not just ignore the fuel warning light?
That gives you full use of the 70L tank you BMW promised you, and the added excitement of not knowing exactly when you are going to creep to a sputtering halt!

Or, you could just fill up when the light tells you. That way, if you ever fall on hard times, you can go crazy on the couple of litres that BMW cleverly kept at arms length.
Those thoughtful Germans.....

[Jobbo]

@drmark: I struggle to see why such a banal post elicits a reply from someone who doesn't care about the issue at all

But it would be useful to know if the capacity really is 70l, not the ~66l which the car is telling me.

[philmots]

hornetrider said:

My E61 is also a 70l tank. I too, am a fuel nazi and don't like filling up too early, hence I run it very low. When the range gets down to zero and I've filled up I've never got more than 66l in it, ergo I have ascertained that there is a ~1 gallon 'reserve'.

So, I won't have any qualms running it 15/20 miles from when the range hits zero.

Excellent, you've just answered the question I was about to ask.

The most I've managed to get in is 63 with 20 miles showing remaining. I assumed the tank was about 66 litres.

[hornetrider]

I did about 15 over zero today and got about 68 litres in

[philmots]

I'm going to start trying this!

Sounds good, sick of going every 270 miles!

[bigdom]

Many years ago, when I had my first 7 - E32 735i it had the extended 100l tank, would have approximately 4 gallons in reserve when it hit zero.

[Wills2]

In an older car especially, you run the real risk of pulling sediments up into the fuel pickup, filter and injectors, I just wouldn't do it.

No gain but perhaps some pain.

[Wills2]

I had 34 miles left on the meter today and brimmed the tank I got 70.73 litres in against a capacity of 80 litres, so I had just over 9 litres or two gallons left which is pretty accurate given the MPG I get round town.