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      03-01-2021, 09:33 PM   #1
ksavostin
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Running X5 45e with no gas in the tank?

Hello, my car just got delivered to the dealership. Since it is shitty outside, I am planning just to keep it in garage until end of April. My dealer is asking me about should they put gas into tank or no?
Can I drive the car to my home just using electric engine with no gas in the tank?
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      03-02-2021, 12:48 AM   #2
bluetriangle
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It'll be fine to keep fuel in the tank until April.

My first tank lasted nine months and I've still got half the tank I put in at the end of August.
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      03-02-2021, 03:35 AM   #3
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Either option will be fine. There will always be a minimal amount of gas in the tank from factory, and if electric range is enough to get you home that will work.
On the other hand, gas is good for at least a year in normal cars, and the X5 has a pressurization system in the gas tank to preserve gas on top of that.
see also this discussion
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      03-02-2021, 03:58 AM   #4
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Better to keep the tank filled, less room for condensation to form.
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      03-02-2021, 04:39 AM   #5
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Quote:
Originally Posted by Drothgeb View Post
Better to keep the tank filled, less room for condensation to form.
the 45e tank is pressurized, which preserves the fuel, unlike conventional fuel tanks.

45e, Ethanol Fuel, and Fuel Degradation over time https://g05.bimmerpost.com/forums/sh....php?t=1761514
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      03-02-2021, 05:17 AM   #6
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Quote:
Originally Posted by nZtiZia View Post
the 45e tank is pressurized, which preserves the fuel, unlike conventional fuel tanks.
That's interesting, I was not aware of this.
Clever since I also sometimes go long stretches with one tank.

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      03-02-2021, 07:56 AM   #7
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This is why we have to press and hold the fuel refilling button, so the tank depressurizes before opening. That button is unique to the hybrids I believe.
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      03-02-2021, 08:04 AM   #8
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exactly, though some folks thought that button actually opened the fuel tank door.
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      03-02-2021, 08:09 AM   #9
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Quote:
Originally Posted by nZtiZia View Post
the 45e tank is pressurized, which preserves the fuel, unlike conventional fuel tanks.

45e, Ethanol Fuel, and Fuel Degradation over time https://g05.bimmerpost.com/forums/sh....php?t=1761514
The pressurization is from fuel evaporation. If you use fuel faster than it evaporates, then outside air containing moisture fills the void. The system does work good. But it’s still better to keep the tank full and stabilize the fuel if needed.
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      03-02-2021, 08:14 AM   #10
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Quote:
Originally Posted by Drothgeb View Post
The pressurization is from fuel evaporation. If you use fuel faster than it evaporates, then outside air containing moisture fills the void. The system does work good. But it's still better to keep the tank full and stabilize the fuel if needed.
how does moist outside air get in to fill the void when the tank is a closed system due to pressurization?
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      03-02-2021, 09:05 AM   #11
Drothgeb
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Let’s say you fill the tank, then go on a long trip in ICE mode, and burn up all the fuel. Something has to fill the void from the missing fuel or, the tank would likely be crushed by atmospheric pressure.

Also, as the fuel is used faster than it can evaporate and fill the void, and pressure drops in the tank, the rate of evaporation will increase. Which is exactly what you don’t want.

I have done some reading on the system. From what I understand, the system is pressurized to prevent gas vapors from escaping. But, there is a control vent on the charcoal canister to allow outside air in to prevent a low pressure situation as I described above. Hopefully the air is dried along the way, but the canister is called a “charcoal” canister not a “desiccant”, so I’m not sure.
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      03-02-2021, 09:30 AM   #12
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I'm just thinking aloud...

so your standpoint is looking at fuel degradation due to condensation from moist air coming in as fuel is consumed during ICE use.

we agree the pressurized tank addresses fuel evaporation. inside while the sitting fuel lets off vapors, it'll get to a point where the pressure inside the tank is high enough to prevent further evaporation regardless of how much fuel is in the tank, but the tank's pressurization doesn't address the possibly condensed air in the "space" above the fuel, which can lead to fuel degradation.

folks in the link I posted earlier stated it was better to have a smaller amount of sitting fuel degrade than a full tank of fuel, but this post seems to address this:

"Yes Im sure about that. G20 and G05 both have pressurized tanks. Official reason for introducing that is for emissions reason: By pressurizing the tank and removing the evaporation system, you are stopping the fuel favors from escaping into the atmosphere. The bonus "side-effect" is that you create a fully sealed system, preventing oxygen and condensation from getting in, thus stabilizing the fuel for much longer periods."
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      03-02-2021, 09:56 AM   #13
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I think we are kinda on the same page.

Evaporation is a bad thing, it leads to fuel degradation. The system uses evaporation to create the pressure to prevent more evaporation. Which is good. But, a lower fuel level creates a larger void, which needs more evaporation to happen to create the pressure that prevents even more evaporation. Now, this is much better than venting the tank to the atmosphere. But, it’s even better to keep the tank fuel, and not leave a void for evaporation or condensation.
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      03-02-2021, 10:35 AM   #14
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I run a PHEV now, would never do so with zero gas, they are not designed to operate as a BEV. It should be fine with a 1/4 tank, but never run on empty. Per Toyota, but applicable to all PHEV systems: "Though a hybrid vehicle can operate in electric-only mode when gasoline is in the tank, it is not designed to run without gasoline. Doing so could cause severe damage to the hybrid system, so drivers should be sure to keep gas in the tank at all times."
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      03-02-2021, 10:52 AM   #15
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Not sure how the X40e does self maintenance/diagnostics but my Chevy Volt would periodically run the gas engine to clear the system and run self checks. Also even if the engine hadn’t been used ~yearly it would run to burn fuel in the system to avoid (I assume) varnish build up in the ICE system.
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      03-02-2021, 10:55 AM   #16
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Quote:
Originally Posted by Stoshu View Post
Not sure how the X40e does self maintenance/diagnostics but my Chevy Volt would periodically run the gas engine to clear the system and run self checks. Also even if the engine hadn't been used ~yearly it would run to burn fuel in the system to avoid (I assume) varnish build up in the ICE system.
I asked this question shortly after taking delivery, but the 45e (can't speak for the previous 40e) doesn't have such a program nor does it require fuel "maintenance" because of its pressurized tank, which stabilizes the fuel longer than the non-pressurized tank in your Volt.
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      03-02-2021, 11:07 AM   #17
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Always good to have correct information, thanks!
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      03-02-2021, 11:33 AM   #18
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more solid discussion points in here:

45e - Gas engine 'run maintenance' ? https://g05.bimmerpost.com/forums/sh....php?t=1783616
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      03-02-2021, 12:04 PM   #19
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Quote:
Originally Posted by Spencer518 View Post
This is why we have to press and hold the fuel refilling button, so the tank depressurizes before opening. That button is unique to the hybrids I believe.
Quote:
Originally Posted by nZtiZia View Post
exactly, though some folks thought that button actually opened the fuel tank door.
Err, I'm sort of in that camp. I knew the tank was pressurized, and that's why it took two presses. I didn't realize it was a hybrid only thing. I thought the 2nd press activated a motor or flap or something to release the pressure. So we're supposed to just press and hold? Just one press and hold?
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      03-02-2021, 12:13 PM   #20
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Yes, press and hold until the instrument display says something along the lines of "Fueling is now possible" Haven't refilled since December, but I think that is what it said.
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      03-02-2021, 12:31 PM   #21
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Haha yeah. With COVID and the electric power, I refuel so rarely I don't remember what happens really.
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      03-03-2021, 05:40 PM   #22
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There’s a one-way valve to let air into the tank as gasoline is used up, or you’d create a vacuum and damage the tank. That incoming air will have some moisture in it, and condensation is an issue long-term. I refilled my tank for the first time after about 6-months...the engine did come on reliably, but I will probably start to put some fuel stabilizer in the tank, but that’s probably not required, but I don’t think will hurt as long as you’re careful about the compounds in the stabilizer.

The fuel pump in BMWs is usually submerged in the tank and relies on the fuel to cool, lubricate, and stabilize it...you really don’t want to actually run out of fuel with a BMW.
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