Full tank vs first click

Sinbad said:
Yes, turning alternators etc can make sparks - as can any cracks in HT leads or similar.
Click to expand...

So why is it they still fill your car?

Shoudent they ask you to turn off your engine first?,

I mean if it can cause an explosion, then why don't they got signs asking you to turn off your engine....
 
eg2505 said:
So why is it they still fill your car?

Shoudent they ask you to turn off your engine first?,

I mean if it can cause an explosion, then why don't they got signs asking you to turn off your engine....
Click to expand...

I've seen signs requesting it.
 
Fill to first click.

The additional space is for fuel expansion and also to reduce the risk of rupturing the fuel tank in an accident. MOST car these days have a venting fuel tank cap.
 
midnightcaller said:
IIRC, the reason why we can't fill out petrol tanks ourselves if because we lack the training to handle the chemical.
The petrol attendants are trained to do this.
Click to expand...

LOL, so you think the populations of the US, UK, Europe etc have to go on training courses before they can use a fuel pump? Overseas a manned pump is a rarity, 99% of petrol stations are DIY.
 
From what I recall the E36 does indeed have an auxiliary tank. The overflow will need to take that into account.
 
Yikes. So many replies.

Back to my original question - every bit of logic tells me it shouldn't, but is there some way that filling to first click reduces your fuel consumption over a totally full tank?

The only answer I could come up with is that there must be some sort of a pressure release that let's petrol vapour out.

In fact there has to be a way for air to come in - the fuel that gets used by your engine is replaced by air in the tank
 
I fill up twice a month and never let it drop below quarter tank. It is cheaper to keep the tank topped up instead of refueling from empty and it greatly increases the service life of the pump by always keeping the tank partially full. I also only fill it until it clicks.
 
This is a thing? I just say "fill up" and let them do what they want.
 
Cyborg said:
Yikes. So many replies.

Back to my original question - every bit of logic tells me it shouldn't, but is there some way that filling to first click reduces your fuel consumption over a totally full tank?

The only answer I could come up with is that there must be some sort of a pressure release that let's petrol vapour out.

In fact there has to be a way for air to come in - the fuel that gets used by your engine is replaced by air in the tank
Click to expand...

1. Your stats will be more accurate if you fill up only to the first click...so your consumption will appear better. If you filled up one tank to the click and the next you overfilled then you would "use" more petrol for similar mileage so the tank that overfilled would appear heavier.

2. There is the vapour exchange airlock story as well...but I highly doubt that will make any more than a 100ml of difference.

thestaggy said:
I fill up twice a month and never let it drop below quarter tank. It is cheaper to keep the tank topped up instead of refueling from empty and it greatly increases the service life of the pump by always keeping the tank partially full. I also only fill it until it clicks.
Click to expand...

How is it cheaper? You still have to travel the same amount of kilometres every month regardless of how you fill up so you'll use the exact same amount of petrol overall.

Not to mention you might be losing money by making unnecessary trips to the fuel station that would be negated otherwise.

Also how is the pump being affected at all based on the level of the thank, disregarding it going completely bare bones empty of course. If anything a fuller tank should make the pump work less...because gravity and more pressure due to volume.
 
thestaggy said:
I fill up twice a month and never let it drop below quarter tank. It is cheaper to keep the tank topped up instead of refueling from empty and it greatly increases the service life of the pump by always keeping the tank partially full. I also only fill it until it clicks.
Click to expand...

The pump is not going to be any less primed at quarter full vs "empty" (as in the engine still runs fine, not bone dry empty)

And you do realise you use the same amount of fuel right? It may be cheaper to fill from quarter to full, but you still using the same overall amount, you're not saving anything.
 
I have always filled up to the brim. The first is when the fuel reaches the tip of the nozzle.

The best way to look at consumption is to look at how many km you get per litre so you dont have to worry about how many litres filled on different fill ups.

I use android app called Car Logbook and track my consumption as km/l and I have noticed I get more mileage per litre when I fill up early morning:

Screenshot_2015-07-08-12-45-50.jpg

Screenshot_2015-07-08-12-48-13.jpg
 
looks like i'm the only one who overfills the car...I even go as far as shaking the car to get more in :)
 
stroller said:
I don't think that fuel stored in an underground tank a few metres underground will be affected by the ambient temperature.
Click to expand...

From: http://www.frihost.com/forums/vt-97955.html

Well, the coefficient of expansion for petrol is 0.00095 C^-1

Using the simple formula b=DV/(V.DT) you get
DV=b.V.DT

(where V is volume, DT is change in temp, b is expansion coefficient and DV is change in volume).

If we work that for a hypothetical case - say 50litres of petrol with a 20 degree change, we get:

DV=0.00095*50*20 = 0.95 litres
Click to expand...

So filling up at 4am on a winters day vs 4pm gets you 1L free, nothing to laugh about
 
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