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      09-27-2020, 09:42 AM   #1
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I don't own a 45e but do own an older boat that is stored 7-8 months out of the year (and doesn't cycle fuel during storage), so I am paying attention to stored fuel degradation and in particular ethanol additives' impact on said degradation. A recent thread about oil changes on 45e highlighted that a typical 45e may have the same fuel in its tank for many months or perhaps even a year.

So, are you 45e owners paying attention to this issue and how?
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      09-27-2020, 12:39 PM   #2
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Originally Posted by LexxM3 View Post
I don't own a 45e but do own an older boat that is stored 7-8 months out of the year (and doesn't cycle fuel during storage), so I am paying attention to stored fuel degradation and in particular ethanol additives' impact on said degradation. A recent thread about oil changes on 45e highlighted that a typical 45e may have the same fuel in its tank for many months or perhaps even a year.

So, are you 45e owners paying attention to this issue and how?
I am not, but maybe I should? I think it will take untill December before I will need to take fuel again. In 6 weeks and 1000 km I only used 17%.

The advised fuel is 95 E10 and max E25. Minimum is 91.

The manual doesn't mention anything about having to empty the fuel tank after a certain interval.

The 45e has a special switch to release the pressure in the tank that could have build up by fuel gasses after long time. It has to be pushed before opening the fuel cap. As far as I understand the manual there is no system building up pressure for fuel quality.
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      09-28-2020, 10:16 AM   #3
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Originally Posted by X5 45e View Post
I am not, but maybe I should?
Well, unless BMW has hid a lifetime supply of fuel stabilizer somewhere in the car, it seems the answer is a resounding YES!

Here is an example short summary article, but there is a lot more information about it online: https://www.hyperlube.com/blog/blog/...soline-go-bad/. I am shocked this hasn't been discussed in detail yet, kind of a big deal for 45e.
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      10-10-2020, 04:38 AM   #4
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I actually find myself deliberately running the ICE from time to time if the majority of my trips are pure electric for a couple of weeks. Does not make economic or environmental sense, but I dread to think what could happen with stale fuel gumming up things 🤷
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      10-11-2020, 12:41 PM   #5
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The fuel tank in most new hybrids (including the 45E) is actually pressurized unit unlike the non hybrid models. This new system was added to preserve fuel and prevent it from degrading over prolonged period of time.
After you fill up and close your tank, the system pressurized the tank and thus makes it stable to be stored for long periods of time.
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      10-11-2020, 12:57 PM   #6
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Originally Posted by MissionPerformance View Post
The fuel tank in most new hybrids (including the 45E) is actually pressurized unit unlike the non hybrid models. This new system was added to preserve fuel and prevent it from degrading over prolonged period of time.
After you fill up and close your tank, the system pressurized the tank and thus makes it stable to be stored for long periods of time.
Are you sure about this? I have been looking for info on this.

I know a button needs to be pushed before opening the tank to release pressure. If I understand the manual correctly it is to release the pressure of gasses being build up. But I don't know if this is done on purpose and actually a system building up pressure or if it is a side effect of not taking fuel for a long time.

On the other hand. Normal cars only doing few miles would have the same issue with pressure building up.

It would interest me to know the details.
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      10-11-2020, 01:02 PM   #7
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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 removinghe EVAP 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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      10-11-2020, 01:17 PM   #8
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Quote:
Originally Posted by MissionPerformance View Post
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 removinghe EVAP 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.
Ok thanks. I was looking for this info

I had a f15 40e before that had the same system.

Edit: did some short research about the pressure in the tank. Normal cars are depressurized and burn the released gasses with the ICE which is not possible when driving all electric.
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      10-12-2020, 01:10 PM   #9
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Quote:
Originally Posted by MissionPerformance View Post
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 removinghe EVAP 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.
If I understand the text above correctly I think that the pressure in the tank increases by the fuel vapors that can't escape because of a valve and not by a pump actively building up pressure in the tank. Or are we saying the same thing? The end result is the same, a pressurized fuel tank.
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      10-12-2020, 01:41 PM   #10
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Quote:
Originally Posted by X5 45e View Post
Quote:
Originally Posted by MissionPerformance View Post
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 removinghe EVAP 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.
If I understand the text above correctly I think that the pressure in the tank increases by the fuel vapors that can't escape because of a valve and not by a pump actively building up pressure in the tank. Or are we saying the same thing? The end result is the same, a pressurized fuel tank.
This is really interesting. While I am surprised I had not seen a prior discussion on this here, glad we got it going.

But here is how I am visualizing it. I am going to use the word petrol to mean gasoline to ensure no confusion with other molecular gasses.

So ... I worry that such a system cannot rely on natural passive pressurization through petrol evaporation because that is relatively slow. In other words, if the tank isn't pressurized by some stability-safe or inert gas (or vacuum sealed immediately upon closing, but a vacuum is probably hard to do with liquid petrol present in the tank), then environmental humid air will be able to enter the tank and at least somewhat defeat the purpose of pressurization. So in that mode, there would need to active pressurization.

Or is petrol evaporation so fast that it can force all other gases out before any damage (oxidation) occurs and can, therefore self-pressurize passively? I would think this would vary by proportion of petrol vs "empty space" in the tank.

Or is the system simply sealed from outside and whatever environmental air that remains caught inside is not enough to cause severe-enough degradation (ie not enough oxidant without a continuous gas exchange with the environment). If this is the case, I wonder why other ICE systems (boats, lawn mowers, generators, etc) with long term fuel storage requirements haven't adopted this mechanism over decades?

The basic question: what's the mechanism by which pressurization forces out damaging gasses while retaining non-damaging gasses?
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      10-12-2020, 01:54 PM   #11
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Quote:
Originally Posted by LexxM3 View Post
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Originally Posted by X5 45e View Post
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Originally Posted by MissionPerformance View Post
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 removinghe EVAP 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.
If I understand the text above correctly I think that the pressure in the tank increases by the fuel vapors that can't escape because of a valve and not by a pump actively building up pressure in the tank. Or are we saying the same thing? The end result is the same, a pressurized fuel tank.
This is really interesting. While I am surprised I had not seen a prior discussion on this here, glad we got it going.

But here is how I am visualizing it. I am going to use the word petrol to mean gasoline to ensure no confusion with other molecular gasses.

So ... I worry that such a system cannot rely on natural passive pressurization through petrol evaporation because that is relatively slow. In other words, if the tank isn't pressurized by some stability-safe or inert gas (or vacuum sealed immediately upon closing, but a vacuum is probably hard to do with liquid petrol present in the tank), then environmental humid air will be able to enter the tank and at least somewhat defeat the purpose of pressurization. So in that mode, there would need to active pressurization.

Or is petrol evaporation so fast that it can force all other gases out before any damage (oxidation) occurs and can, therefore self-pressurize passively? I would think this would vary by proportion of petrol vs "empty space" in the tank.

The basic question: what's the mechanism by which pressurization forces out damaging gasses while retaining non-damaging gasses?
That is the question indeed. Interesting discussion.

How I understand from the text I found is that:

When depressurizing a normal fuel tank gasses are released and burned by the ICE. This is not possible when driving all electric and furthermore it can't regen the filter. I don't know if this is a safety measure (release of combustible gasses and electricity) or an environmental measure, or both.

A valve keeps the evaporated petrol gasses inside and this builds op pressure until a certain point where the pressure is so high that evaporation stops.

In this text it doesn't mention that pressurization has a positive effect on long term fuel quality (but that doesn't mean it isn't true)

I think it is a passive pressurization.
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      10-12-2020, 03:00 PM   #12
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http://publications.lib.chalmers.se/...063/238063.pdf

If you like some reading. It confirms fuel degradation.
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      01-24-2021, 12:16 PM   #13
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How long between tanks are any of you going? We could go 3-6 months at our rate of EV usage.
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      01-24-2021, 12:38 PM   #14
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I read an article saying that E10 fuel would be less ideal for long storage. For the fuel it self but also alcohol interacting with rubber / metal components of the car.

When driving a lot of electric miles and keeping the fuel for a long time it would be better to go for 98 E5, it can have up to 5% bio ethanol but in practice apparently is doesn't have any.

I didn't refuel from august till end December. Then I did some road trips but know I have a full tank since 1/1/21 and with Covid restrictions I think it will be full for a couple of months again. So I took 98 E5.
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      01-24-2021, 12:41 PM   #15
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Quote:
Originally Posted by IS350 View Post
How long between tanks are any of you going? We could go 3-6 months at our rate of EV usage.
Between road trips I don't have to refuel. And with COVID restrictions family and friend visit are impossible and ski holiday is cancelled.

So I can be 3 - 6 months between fuel stops like you mention.
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      01-24-2021, 01:04 PM   #16
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This is a very good point so what I will do is never fill the Tank so it stays fresh. Unless on a long trip of course I will fill up. I can see myself using the ICE a lot as I have a heavy right Foot.
I didn't buy the Hybrid for efficiency but I do like the fact that it can run on electric around town and that. I will charge every night
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      01-24-2021, 02:24 PM   #17
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Quote:
Originally Posted by 45e X5 View Post
This is a very good point so what I will do is never fill the Tank so it stays fresh. Unless on a long trip of course I will fill up. I can see myself using the ICE a lot as I have a heavy right Foot.
I didn't buy the Hybrid for efficiency but I do like the fact that it can run on electric around town and that. I will charge every night
The article said that it was better to keep it filled up that way less fuel can evaporate

And if the fuel has really been standing too long putting some new fuel should solve the problem (not with a full tank)

From my experience: I have been driving around with half a tank of fuel for 4 months and only driving electric. When I did a longer trip after 4 months and emptied the tank in 1 trip I didn't experience any problems.
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      01-24-2021, 10:21 PM   #18
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If the vapors can escape the tank, the octane level will decrease, but in the X5, the system is sealed, so that isn't an issue. There's an issue with phase separation, but some of that is worse if moisture can get in. Now, as the fuel is used, some air must come in, or you'd create a vacuum, and that won't work, so some air with whatever moisture it may contain, will be getting into the tank over time.

It's been 4+ months since I got my vehicle, and the tank is about 1/2-full. I did buy some fuel stabilizer, but haven't put any in. The few times I've needed the ICE, it did start and ran without issues, so maybe that isn't a real issue with this system.

On the Rotax engine that was on my gyroplane, they allow E10, but they say to use it within 2-weeks of pumping it, or the octane may degrade enough to become a problem. But, in a plane, the fuel tank must be open so fuel can flow, or the pump will not be able to overcome the suction as it's pumped out of the tank. That isn't the issue with the 45e.
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      02-07-2021, 08:29 PM   #19
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It's organic. Fuel degrades due to four key factors: evaporation, oxidation, additive degradation and sludge formation. As a result, the octane number decreases by one or two units, while the amount of resins increases due to the oxidation of hydrocarbons. One of the clear signs of bad gasoline is discoloration. As a rule, expired fuel darkens - instead of pale yellow it becomes brownish.
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      01-21-2022, 10:12 AM   #20
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Quote:
Originally Posted by 45e X5 View Post
This is a very good point so what I will do is never fill the Tank so it stays fresh. Unless on a long trip of course I will fill up. I can see myself using the ICE a lot as I have a heavy right Foot.
I didn't buy the Hybrid for efficiency but I do like the fact that it can run on electric around town and that. I will charge every night
Isn’t one of the ways to mimimize ethanol evaporation to keep the tank full?
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      01-21-2022, 10:59 AM   #21
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Quote:
Originally Posted by castcore99 View Post
Isn’t one of the ways to mimimize ethanol evaporation to keep the tank full?
ethanol evaporates at 78 degree C no matter what the tank capacity is.

are you concerned about water in the fuel? that's a different property altogether. ethanol absorbs water from the air, so the traditional thinking is the more air in the tank, the more water can be absorbed by the ethanol in the fuel. therefore, keeping the tank full reduces the amount of air thus reduces the amount of water that can be absorbed.

keep in mind the 45e fuel tank is sealed and pressurized, so traditional thinking doesn't apply.

Last edited by nZtiZia; 01-21-2022 at 11:08 AM..
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