Gas in Tank

Discussion in 'Clarity' started by ClarityMark, Jun 18, 2018.

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  1. ClarityMark

    ClarityMark New Member

    How long can gas sit in the tank before fuel stabilizer should be added and/or drive gas-only for a while so new fuel can be put in? We've had our Clarity for two weeks and haven't used an ounce of gas, which made me realize this morning that we could easily go a few months without needing to re-fuel.
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  3. Tahuna

    Tahuna Member

    With my previous PHEV, a Ford C-MAX Energi, they explained that the car removed the air from the gas tank in order to preserve the gas. Because of that, when you wanted to fuel the car you had to hit the fuel door button and then wait for it to say it was ready.

    The Clarity doesn't say anything at all about removing air from the tank - but it does have the delay from when you push the fuel door button to when it actually opens the fuel door. This makes me think they may do something similar, but I'm not sure.
    chris5168 likes this.
  4. ClarityMark

    ClarityMark New Member

    I'd ask my dealer but they are pretty clueless when it comes to this car.
  5. KentuckyKen

    KentuckyKen Well-Known Member

    There is great difference of opinion on the internet as to how long it takes untreated gas to deteriorate. I’ve seen it listed as little as 30 days and as long as a year. There’s is also much misinformation on the subject to boot.

    There is no doubt that the gas in your lawn mower tank or refill tank in your garage will go bad much sooner than that in your car’s sealed gas tank. But that doesn’t mean that long term storage in your car’s tank is OK.

    Before going down this rabbit hole, I offer a short primer on gas. Gasoline is a highly refined petroleum product that can deteriorate mainly by 3 mechanisms. It can oxidize, lose volatility, or be affected by moisture.
    1 Oxidation: The oxygen in the air causes slow breakdown of the complex hydrocarbons. Entropy reigns supreme. In severe cases or longer time, it can result in varnish build up and discolored smelly gas. But even before the gas gets that bad it will have changed into lesser compounds from what you paid for and from what the engine is tuned to work with. And varnish build up is a cumulative process best avoided.
    2 Loss of Volatility: The more volitile compounds will evaporate faster altering the gas’ very important volatility index. Refineries track this very carefully and it is the reason why there are different formulations for summer and winter.
    3 Effects of moisture: While gas and water don’t mix, most gas has some ethanol content and ethanol readily absorbs water (think gin and tonic) and this combination is corrosive to engine parts.

    So what does all that mean and what should we be doing about it? Here’s my 2 cents (and you get what you pay for).
    An ounce of prevention being worth a pound of cure, I’d say that a bottle of Stabil is many times cheaper than any potential injector or fuel related problems. And one bottle will treat 3 7gal tanks in our Claritys. Since I’m only adding it once or twice a year that only costs $2 or $4 a year.

    Ah, but some will say our gas tanks are pressurized or sealed and indeed they are and this does reduce the evaporation and volatility reduction, but does not eliminate it. When your tank is not full, it has from 1 to 6 gallons volume of air for the volitile components to evaporate into. And that air is going in and out of the tank as the gas goes in and out.
    This air volume in the tank is also full of its moisture and oxygen and the gas is exposed to both. So the potential for trouble for those of us who primarily drive in EV and seldom has ever trips in HV, I think is a valid concern. For example I have only used 2 gal of gas and none in the last 4 months. Anticipating this, I added Stabil back in Feb (and ran a little to get it to the injector) and it will keep my gas good till I take a trip latter this summer. Of course if you regularly have HV trips then you don’t have to worry.
    Now what about full tank vs just keeping 2 gal to reduce the “dead” weight by 30 lbs or so? Like everything else in life, it’s give and take or risk vs gain. I keep my tank full to reduce the possibility of condensation, evaporation and oxidation and live with the very slight reduction in mpg from adding 30 lbs of fuel to a 4,000 car.

    So I will go out in a limb and say if your HV occasions are spaced out with 6 months (or more) between or you aren’t adding a tankful every 6 months, then I would add the Stabil. At least that’s what I’m doing while we wait to see if our Claritys are programmed like the Volt to not allow gas to become more than 1 year old.
    As always, YMMV
    And I am not a petrochemical engineer and don’t pretend to be one. This info is from several well known publications on the net.
    HGTZ, Robin, insightman and 1 other person like this.
  6. dstrauss

    dstrauss Well-Known Member

    Downsides to Stabil?
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  8. ClarityMark

    ClarityMark New Member

    Thank you for taking the time to provide this detailed reply. Very helpful/
  9. qtpie

    qtpie Active Member

    A different question on same subject.... since we fill up less often on Clarity PHEV, should we put premium gas with higher octane instead of regular gas so that it would last much longer when we need it? Thanks.
  10. insightman

    insightman Well-Known Member Subscriber

    Does premium gas last longer than regular?

    I'm going to follow advice I read on this Clarity forum and spend even more than premium for ethanol-free gas. When I finally have to buy gas, that is.
  11. Viking79

    Viking79 Well-Known Member

    Octane decreases with age, premium theoretically can age longer before dropping below a threshold where it is a problem. However, I am having issues finding studies to show how much it drops in a pressurized container. I don't think it would matter less than 1 year.
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  13. Steven B

    Steven B Active Member

    My unscientific opinion is that premium will burn better when you do run it through the engine and hopefully keep it cleaner than burning regular. Additionally, even though Honda says regular, the compression ratio is quite high and in the past, ratios this high needed premium to prevent knocking.
  14. For best economy, people should use the gasoline with the lowest octane that meets the car's specifications.
    The higher the octane, the less energy per given mass/amount.

    Octane increases over shelf life. But, gasoline is extremely complex. So, that increase in octane is a "statistical thing", not anything that is useful for a gas engine.

    To make it more involved, if I recall correctly, there are around a dozen+ versions of gas sold over the year in the Continental US. If someone used (new)summer Southern Calf in Northern Maine in February, they would likely have a hard time starting their car - if the car was outside, and temps were below 0F.
    Last edited: Jun 18, 2018
    KentuckyKen likes this.
  15. I wanted to get the first post in, in case posting web links makes this post wait for approval.

    First the links, then the pasted text so that people don't have to download the PDF and read it (a hassle for those on mobile devices :).
    Lifetime of Fuel.
    This Fuel News provides a guideline on fuel storage in small containers from handy cans to fuel tanks of equipment.
    Loss of light components – impact on octane.
    The light components in petrol are lost first as the petrol sits in the fuel tanks.

    Lifetime of Fuel.
    Fuel News
    Lifetime of Fuel

    This Fuel News provides a guideline on fuel storage in small containers from handy cans to
    fuel tanks of equipment. It only covers quality issues and does not address safety and
    legislative issues around storage. For safety and legislation refer to the latest issue of
    Australian Standard 1940.

    For domestic use fuel should be stored in steel cans of 2.5 litres, 5.0 litres or in 25 litre jerry
    cans. Plastic containers of the approved type with the Australian Standards mark (AS2906-
    1991) on the bottom can also be used.

    Volatile fuels such as petrol and two stroke mixes will store for up to one year in a sealed
    container. After that period the fuel may still be fit for purpose but problems such as hard
    starting and spark plug fouling may occur due to lack of light components.
    Once the seal is broken then lighter components evaporate and the storage life is best
    assumed to be 6 months at ambient temperatures of 20 deg C and 3 months at ambient
    temperatures of 30 degrees C or more.

    Petrol and two stroke mix in a fuel tank is exposed to the air and lighter components will
    readily evaporate. This will result in the fuel becoming heavier and will cause hard starting
    and spark plug fouling and rough running and misfire because the fuel will make the air fuel
    mix richer in fuel, not all of this fuel can be completely burnt so it will leave sooty deposits in
    the combustion chamber. For this reason any petrol and two stroke mix which has been in
    the equipment tank for more than 2 weeks at 30 deg C or higher should be used with
    caution. Volatile fuel that has been in equipment fuel tanks for more than two weeks should
    be freshened with an equal volume of new fuel to restore volatile components and reduce
    fouling issues.

    Keeping equipment fuel tanks one third full stops moisture from getting into the fuel tank and
    leaves room to add fuel to freshen the mix. Safety concerns need to be addressed when
    keeping equipment tanks partially full while not in use.
    BP fuels contain anti oxidants to stop fuel from deteriorating and forming gums, they contain
    metal deactivators to prevent corrosion of copper and brass fuel system components and
    detergents to clean fuel systems of deposits that interfere with performance.
    BP Ultimate also contains a corrosion inhibitor to keep steel lines and components free of
    rust and the higher octane provides protection against octane loss during storage.

    Diesel is not volatile and so does not suffer from starting issues. When stored under cover in
    sealed containers it will last for 1 year but it can last longer. The main issue with diesel fuel in
    storage is formation of gums and sediments that block filters, this is associated with
    darkening in colour.

    The main problem with diesel fuel in opened containers is that moisture from condensation
    Will create a favorable environment for fungus and bacteria that degrade the fuel. The
    Simple solution is regular treatment with a biocide. (Every 6 months)
    For further information, please call the BP Lubricants and Fuel

    Loss of light components – impact on octane.
    Fuel News
    Petrol Life in Vehicle Tanks

    Petrol is a mixture of many components with different properties that contribute to the
    performance of the fuel. When petrol is left out in an open container exposed to the air it will
    in time completely evaporate. As it evaporates the composition and properties will change
    because different components evaporate at different rates. This is a normal feature of petrol
    and the same process takes place in equipment fuel tanks. Where petrol is kept for more
    than a week in equipment tanks then it can become stale and it is better to add fresh fuel
    before using. Examples are classic, veteran and vintage cars and bikes, racing cars and bikes,
    drag cars, boats, dual fuel vehicles, lawn mowers etc.

    Generally petrol will last in equipment fuel tanks for about 3 weeks at a temperature of
    around 20 deg C, after that it will perform better when fresh petrol is added.
    Petrol will last in sealed containers for more than 6 months, while some breathing will take
    place this is not enough to significantly affect product quality.
    In underground storage tanks the rate of replenishment prevents the fuel from becoming stale.

    Loss of light components – impact on mixture
    The light components in petrol are lost first as the petrol sits in the fuel tanks. These
    components provide valuable octane benefits during cold start. Because they are
    volatile they compose most of the air fuel mixture during cold start, if they are absent
    then the mixture becomes lean resulting in higher temperatures, pre ignition,
    detonation and piston damage. This is generally the cause of piston damage in high
    revving engines used in boats and small engines such as chain saws etc.
    The portion of the petrol that remains has a higher density and higher octane but this
    is not available during cold start resulting in hard starting. Because the fuel
    carburetors and injectors operate on a volume metering system the higher density
    means that more fuel is introduced for a given volume of air and so the air fuel ratio is
    fuel rich. If all the fuel cannot be burnt then it forms carbon deposits that will foul the
    spark plug and cause the engine to stop and not start. This is generally the cause of
    problems in classic cars where the engine stumbles and hesitates or cuts out.

    Loss of light components – impact on octane
    The light components in petrol are lost first as the petrol sits in the fuel tanks. These
    components provide valuable octane benefits under high revving conditions such as
    cold start acceleration and the loss of these components can result in detonation and
    pre ignition at high speed resulting in piston damage.

    The remaining components that have not evaporated are high octane and octane can
    actually increase with time but this octane is not available for high revving

    Gum and Peroxide formation
    With long storage periods, especially in the presence of hot weather or engine heat the
    petrol can oxidize to form peroxides. These compounds can attack rubber and metal,
    stripping away the liner on fuel lines or copper from fuel pumps and attacking rubber
    hoses. These normally take a few months to form in sufficient quantity to cause a
    problem. This process is faster if Ultra Violet light can get to the petrol.

    Volatility restrictions

    Current State EPA legislation restricts petrol volatility in the summer period,
    generally November to March. In that period petrol will have less volatile
    components than at other times, generally the summer volatility of petrol is 30%
    lower than the winter volatility which means that the loss of lighter components in
    summer can be quicker. However this is not usually an issue due to higher
    temperatures but can create problems in autumn if the summer fuel is held over. To
    avoid this fresh fuel should always be used in the April May period.

    It is not possible to provide a foolproof strategy for engines that are used only intermittently,
    however the following principles help.
    1) Always add some fresh fuel when the equipment is to be used if it has not been
    used for more than a week. This will provide additional volatile components and
    protect from cold start high revving detonation and piston damage.
    2) Always keep the tank half full to stop water vapour from being sucked in and
    3) Use a fuel that contains anti oxidants, metal deactivators and corrosion inhibitors to
    protect metal surfaces such as BP Ultimate
    4) Using a hotter spark plug will help to reduce carbon deposits

    Week 1 Week 2 Week 3 Week 4 Week 5
    % volume lost
    3 5 8 10 15

    Octane RON
    98.1 98.4 98.6 99 99.5

    Equivalent airfuel ratio atconstant volume
    13:1 12.8:1 12.7:1 12.5:1 12.3 :1

    At the end of 5 weeks the fuel is 5% heavier and the fuel air mix will contain more fuel.

    I hope the above helps! :)
  16. Viking79

    Viking79 Well-Known Member

  17. PHEV Newbie

    PHEV Newbie Well-Known Member

    I'm old school but I was always taught never to leave an internal combustion engine completely off for long periods. I suggest going into HV mode when you're on the freeway at least once every week or two to get the ICE to operating temp. That way, you'll keep the ICE well lubricated and contaminants from accumulating in the oil from non-use. If you do this routinely, the gasoline will never get old enough to cause any damage to the ICE and you'll keep your whole system healthy for the long term. This is a PHEV so you have to care for it differently than you would for a BEV.
  18. Interesting! :)
    I've always heard/believed that since the light volatiles are the first to dissipate, that leaves more heavy volatiles and hence, the "rise" in octane.
    I think it also has a lot to do with the mixtures, the ethanol, and the octane enhancers used.

    I will agree that for all practical purposes, the "useful" octane/power goes down with age. :)
  19. KentuckyKen

    KentuckyKen Well-Known Member

    I don’t see how air can be removed from a fixed volume steel gas tank as the fuel is consumed unless it has a bladder inside. Otherwise the tank would implode if the pressure was reduced enough. As the gas is pumped out, air has to enter to replace the equivalent volume of gas leaving. This is what introduces the moisture and oxygen content of that incoming air. The more fuel in the tank the less air in the tank.
    I think you are talking about the slight pressure differential maintained in the tank that when brought to ambient pressure by a misplaced or leaking gas cap will set off the check engine light. It can’t keep the air out but shows the tank is properly sealed and is reducing the excessive evaporation of volitiles and condensation of moisture that an open system would have. It also has a positive effect on the environment by keeping gas fumes from escaping and this is why you can sometimes find pumps with an accordion sleeve to seal the connection when you gas up to prevent this.
    Can’t find the reference for this so feel free to correct me if I’m in error.
    Last edited: Jun 18, 2018
  20. It's because of the pollution control requirements on gasoline evaporative emissions.

    It started in the 70's. Before, the gas cap was vented to the outside world. So, the gas tank was always at the outside air pressure.
    As we've been talking about, gasoline evaporates.
    Back in 60's, gasoline evaporated a lot more. Gas was cheap, pollution wasn't as big of a concern.

    Starting in the 70's, the gas tank and fuel system were kept as a "sealed" system.
    Many cars back then, just ran engine vacuum to the system (~15psi). So, when people took off the gas cap, they would hear the common "hissing" of air going into the gas tank.

    Now, we're smarter, and the systems are more complex.
    Today, the gas caps have pressure and vacuum relief valves in them.
    Tanks are kept at a lower vacuum, but still under vacuum.
    Also, systems have vacuum sensors in the gas tank or system. I think that's a requirement for the OBD-II tests.

    Some links and snippets:
    Evaporative Emission Controls
    Changes in atmospheric temperature cause fuel tanks to breathe, that is, the air within the tank expands and contracts with outside temperature changes. If an unsealed system was used, when the temperature rises, air would escape through the tank vent tube or the vent in the tank cap. The air which escapes contains gasoline vapors.

    The Evaporative Emission Control System provides a sealed fuel system with the capability to store and condense fuel vapors. When the fuel evaporates in the fuel tank, the vapor passes through the EVAP emission valve, through vent hoses or tubes to a carbon filled evaporative canister. When the engine is operating the vapors are drawn into the intake manifold and burned during combustion.

    A sealed, maintenance free evaporative canister is used. The canister is filled with granules of an activated carbon mixture. Fuel vapors entering the canister are absorbed by the charcoal granules. A vent cap is located on the top of the canister to provide fresh air to the canister when it is being purged. The vent cap opens to provide fresh air into the canister, which circulates through the charcoal, releasing trapped vapors and carrying them to the engine to be burned.

    Fuel tank pressure vents fuel vapors into the canister. They are held in the canister until they can be drawn into the intake manifold. The canister purge valve allows the canister to be purged at a pre-determined time and engine operating conditions.

    Vacuum to the canister is controlled by the canister purge valve. The valve is operated by the PCM. The PCM regulates the valve by switching the ground circuit on and off based on engine operating conditions. When energized, the valve prevents vacuum from reaching the canister. When not energized the valve allows vacuum to purge the vapors from the canister.

    During warm up and for a specified time during hot starts, the PCM energizes the valve-preventing vacuum from reaching the canister. The EVAP purge control solenoid begins to operate when the engine coolant temperature reaches a predetermined operating temperature.

    Once the proper coolant temperature is achieved, the PCM controls the ground circuit to the valve. When the PCM opens the ground, this allows vacuum to flow through the canister and vapors are purged from the canister into the throttle body. During certain idle conditions, the PCM may energize the purge valve to control fuel mixture calibrations.

    The fuel tank is sealed with a pressure-vacuum relief filler cap. The relief valve in the cap is a safety feature, preventing excessive pressure or vacuum in the fuel tank. If the cap is malfunctioning, and needs to be replaced, ensure that the replacement is the identical cap to ensure correct system operation.

    The following components are part of and affect the operation of the EVAP (Evaporative Emission) Control system:
    Fuel Tank
    Fuel Fill Cap
    Evap Two Way Valve
    Evap Control Canister
    Evap Three Way Valve
    Fuel Tank Pressure Sensor
    Powertrain (PCM) Control Module
    Evap Purge Control Solenoid Valve
    Evap Control Canister Vent Shut Valve
    There are a lot of us with gas tank pressure problems and various problems related to fuel pumps.
    Here are the symptoms my car (1982 Camaro with cross-fire, 45,000 miles) had:
    1.Idle too low
    2.Engine would die at stoplights
    3.Incredible pressure in the gas tank, only relieved by removing the cap
    4.A very loud humming/whining/droning sound coming from the gas tank. This sound is almost like a fog horn and comes from under the back seat. The sound would continue with the key off, and would stop when the gas cap was opened and the pressure released

    Repairing the evap system (about $40) cured all of the symptoms listed above.

    My car is a 1982 with crossfire fuel injection, other years may be slightly different, but the basics are the same. The EVAP system is incredibly simple, it is easy to test and fix and there is absolutely no reason to remove it.

    There are three moving parts that can go wrong under the hood with the vapor recovery system, (1) the canister intake vacuum valve, (2) the canister outlet valve, and (3) the evap canister solenoid (which controls the canister outlet valve).

    The canister intake valve is mounted in the line from the gas tank and is about 6 to 8 inches from the canister. It is on left hand side with the yellow hose clamps in the photo below. The canister outlet valve is in the center on top of the evap canister, and the evap canister solenoid is mounted on the fender to the right. (Sorry about the dates on the photos, didn't see that until I was posting this)

    There is a lot of misinformation about the cannister inlet valve in some other threads. This valve is CLOSED when the car is off. Gas vapor cannot escape the gas tank to the canister or the engine when the car is off. As soon as the car starts and vacuum is applied to this valve it is supposed to open. So, the normal condition for this valve is closed when the car is off, and open when the car is running. The purpose of this valve is to let gas vapors into the evap canister when the engine is running, that’s it. Very simple to test, just hook up a vacuum tester and blow through the valve. It should flow air easily with a just a few psi of vacuum applied and it should hold the vacuum and not bleed down. If it doesn’t open or won’t hold a vacuum, replace it. These are readily available all over the place from Standard Products. The photo below is this valve with a vacuum tester on it. My cannister inlet valve was OK.

    I hope the above helps.
    leehinde likes this.
  21. KentuckyKen

    KentuckyKen Well-Known Member

    Thanks, GrayRed, great info and it’s how I remember my old cars used to roll. My point was that even with a sealed system under some negative pressure, there is still some air in the tank as it is never a total vacuum and when gas is added the tank must be at ambient pressure with air making up the difference between tank capacity and amount of fuel present. So even with the charcoal and sealed system negative pressure, some oxygen and moisture can get to the gas. But the system certainly reduces it compared to the vented cap on your lawnmower. But it doesn’t eliminate it. Hence, the need for Stabil if it sits in the tank for extended periods; especially if the tank is low with a high air volume.

    The question becomes how do you define the extended storage time that would benefit from and trigger the use of Stabil? And do you want winter formulated gas used in the summer and vice versa?
    Since I’m in track to go 6 months before using any gas (Don’t take many trips out of town), I’m erring on the side of caution and using Stabil and between seasons (2x/yr) using a tank in HV mode, unless I go on an HV trip.
  22. WOW!!!!!!!!!!!!!!!

    The answer varies depending on where a person lives, the type/version of gas they use, and so on.
    Imho, the short answer is use a 4oz bottle of Sta-bil (~$6) once a year, if someone goes through less than an average of 1 gallon of gasoline per month.

    Imho, using Summer gas in the winter, here in New England, is not a good idea.
    Imho, it's noticeable on snow blowers and older cars (with carburetors).
    But, that's assuming that the car/snow-blower is kept outside and it won't have any benefit of any sun.

    There are parts of the Country where it gets much colder than here in New England. So, it's even more important for them.

    Then, we have the Southern Calf, Texas, and Florida people. Northern parts of Texas and Florida see temps below 32F for only a short time. So, even with "old summer gas", most decent running engines will start fine.

    Imho, the varnish from old gasoline can often more of an issue than loss of light volatiles.
    Also, that brings up another important point, using a top quailty gas is even more important.
    So, imho, use Mobil or Exxon.
    Disclosure: My friend's father owned an Exxon station when I was a teen.
    Hence, being a gear-head and getting engineering degrees.

    I use Sta-Bil in my lawn tractor for when it sits during the winter. And, for my snow blower, for when its sits during most of the year.
    Imho, a 4oz can of Sta-bil is fine. It won't hurt anything. Actually, Sta-bil says that 1 ounce will treat 2.5 gallons.

    I hope that the Honda engineers have programmed the engine (ICE - I hate that term :)) to run enough so that the ~7 gallons of gas that can be held in the tank, get used before "x-amount of time".

    There is the Built-In-Test (BIT) of the engine and the associated charging/power system.
    That could be programmed:
    a) To run after at least x-number of car running minutes.
    b) To run after at least x-number of car trips.
    c) To run after at least x-number of days.
    d) They could also program the engine to use x-amount of gas within y-amount of "days".

    But, it seems from your experience, and I think 1-2 others form what I've read in the past month, the Clarity can go a while without using much gas.

    I do agree, that with the Clarity, I can see a number of cases where people could use battery power almost all the time.
    Imho, for those people, my suggestion is to spend ~$6 a year on Sta-bil. That's less than the cost of 2 gallons of gas.
    Again, varnish from old gasoline can often more of an issue than loss of light volatiles. At least here in New England. :)

    Since I live in hilly New England, and have a longer commute (and I don't have the option to charge the car at work), I don't have to worry that I'll use less than 1 gallon per month.
    KentuckyKen likes this.
  23. Johngalt6146

    Johngalt6146 Active Member

    I worry about this also, since my ICE has not been on since Feb.

    I do recall my experience with my wife's recently sold 1967 Camaro 6 CYL 2 bbl car:
    - If I started it every 4 weeks or sooner, never a problem.
    - If I waited to 6 weeks, it required ether in the Carb. to start.
    - I bought gas (regular) about every 2 years.

    I think I'll force an ICE start of my Clarity at 6 months, if the computer has not done it before then.

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