How often should i run the gas engine

Discussion in 'Prime Main Forum (2017-Current)' started by MarkP., Jun 8, 2020.

  1. MarkP.

    MarkP. New Member

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    I have only seen one post on this question and not a lot of responses, i might have missed other posts. This is my first post here on Prius Chat.

    I have a 2018 Prius Prime that I have owned for about 27 months. I live in the southern Nevada. Only info I can find in the owners manual on gas usage is that 5 1/2 gallons of gas should be added a year. Not seeing anything about how often to run the gas engine.

    I work from home and am almost retired, my wife is retired so the car is only used for pleasure. This is our only car. We drive an average of about 600 miles a month but almost every day we take a drive. Our driving routine usually take us no more than 5-10 miles from home. Last few months our usage has been about half of normal and less often.

    First year anniversary owning the car i added 5.75 gallons, at about 16 months we took a 3600 mile road trip. Trip meter showed 62.5 miles per gallon for the road trip. Last time i filled up was on Aug 17, 2019. Tank still looks to be about 7/8 full.

    At times I could easily go several months between using gas. When I first got the car, if I did not use gas one month I would make sure I flipped the switch and used gas for a trip or two in the next month. Lately I have started using gas a little more often, but we are hardly ever more than 10 minutes away from home so not much gas is used. Our most usual trips contains local driving then I jump on the freeway for several miles and back off again. Today we took a different drive and was low on charge and the gas engine ran for about 6 highway miles.

    I asked several service guys at the Toyota dealer on running the gas engine, asked them how often and how long the drive should be and received various answers. I have had zero issues with the car so far, I just want to make sure I do not do permanent damage to the car by not running the gas engine enough.

    Questions for the group are:
    1) How often should I run the gas engine.
    2) When I do use the gas engine, should i make sure the trip is a certain length, i.e. x miles of highway driving, etc.

    Thanks in advance for any responses.
    Mark
     
  2. Washingtonian

    Washingtonian Senior Member

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    Mark - There are two things to keep in mind. First, gasoline has a definite shelf life. After a few months, maybe three to six, particularly if has ethanol added, it becomes stale and may also have taken in some water from condensation. It is a good idea to use the gas before that happens. Second, it doesn't help an engine for it to sit unused for six months to a year or longer. If you had a classic car in your garage, you would make sure to start it and run it long enough for it to lubricate the moving parts and drive off the condensation in the oil at least every 3 months or so. If it had sat a year or longer you would turn it over with the coil disconnected to makes sure oil pressure was up before starting it. That said, no one can give you a definite answer on how often to run the engine or how long to run it. Some might suggest you keep a minimal amount of gas in the tank so you can get slightly better mileage from the lower weight of the car. Some might tell you to only charge the traction battery just before you plan to use the car. My suggestion is to just drive and enjoy it.
     
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  3. bisco

    bisco cookie crumbler

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    different engine, but mine exercises every 124 miles if i don't use it. i just let it finish its warm up before shutting down.
    normally, i would only keep a couple gallons in it, because i don't drive beyond ev range all the much, but i put 8 gallons in just before the lockdown, and now i'm gonna have to burnit off needlessly by 9/15.

    if i had a prime, i would just use the minimum amout of fuel the manual recommends, and not worry about the engine.
    seeing that toyota ditched the automatic 124 mile exercise, they must feel it is unnecessary. and using the minimum amount of fuel every 6 months is sufficient engine run time.

    i might run it out on the highway for 10 miles or so every 6 months, if it wasn't getting any high speed usage, but that might just be old fashioned thinking.
     
  4. fuzzy1

    fuzzy1 Senior Member

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    That is a old-era answer for unsealed and vented gas tanks, as was the norm on cars more than a generation ago, and still is the norm for common gasoline powered appliances around the home and yard.

    But modern evaporative emission control requirements (EPA) have lead to much better sealing in all recent cars (U.S.-market), so gas in them lasts much longer. And the PHEVs have stepped up their game to a level higher than regular gassers, so they can go longer still without problems from evaporation, oxidation, or moisture accumulation. If you follow the Toyota Owner's Manual, you will be fine. GM programs it in to their PHEVs, so it is taken care of automatically.

    Here are some of my past replies on this topic:
    Concerned over gas going bad | PriusChat
    Breaking the fill-up habit | Page 2 | PriusChat

    Further back, I posted a calculation of how much moisture could come in with the make-up air as the fuel level drops. That amount is far less than what E10 is able to handle when acting as a gas line drier / de-icer, something people used to deal with by adding HEET. It takes additional air circulation, exchange with the outside atmosphere, to bring in enough moisture to be a problem. The Prime's well sealed tank should be safe from this for a fairly long time.
     
    #4 fuzzy1, Jun 8, 2020
    Last edited: Jun 8, 2020
  5. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Just a seat-of-pants thought: have a "hybrid day" at least once a week, and aim to go through a tank of gas at least tri-monthly.
     
  6. sam spade 2

    sam spade 2 Senior Member

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    You need to run it often enough and long enough to use 5 1/2 gallons a year........minimum.

    Personally, I would try to do that about every 3 months and run it down past 3/4 empty before filling.
    That would end up being about 10 gallons every 6 months.
    The engine needs to run long enough to thoroughly warm up. 5 miles minimum....maybe.

    There is no need to be obsessive about NOT using gas.
    With the price where it is now, the cost difference probably isn't that much.

    How do you account for the fact that some components of a modern gasoline mixture will deteriorate over time even if stored in a perfect vacuum ?

    And if it picks up contaminants before entering your tank, that can happen even faster ?

    How about quoting some actual authoritative sources instead of opinions from an Internet forum ??
     
    #6 sam spade 2, Jun 8, 2020
    Last edited by a moderator: Jun 8, 2020
  7. Tideland Prius

    Tideland Prius Moderator of the North
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    The manual states to add a total of 20L (5 1/4 gal) within a 12-month period and given that Toyota is a conservative company, I'd imagine that would be ok. The Prime does have a pressurized fuel tank (part of the zero evaporative emissions package) so gas probably can stay "fresh" longer than in a regular car.

    I did an experiment last year and went 76 days without the engine coming on. It ended because I went on a road trip. I was seeing if Toyota has a built-in engine run time counter but it never came on on its own accord.

    If you wish, you could run it in hybrid mode for an entire month every year or for two months out of the year if it helps alleviate your concern.

    I would try to vary the rpms when you're running so a highway run may not necessarily be a good thing (even though it will get the temperature up to operating temperature sooner).. maybe combine a highway run to get it up to operating temperature with a city drive to help vary the rpm.
     
  8. fuzzy1

    fuzzy1 Senior Member

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    Why do you assume that Toyota didn't account for this?

    BTW, in a perfect vacuum, evaporation not only continues, but is accelerated. Evaporation is one of the problems that changes the gasoline.
    How about you reading the sources I have previously posted? The relevant section of the Prime's Owner's Manual is just one of the items I have quoted or linked.
     
  9. sam spade 2

    sam spade 2 Senior Member

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    If it is an enclosed space, that only happens for a few seconds.......until the space becomes saturated with the vapor.

    Anyway......like with a lot of other things, I think it is better to err on the safe side.
    Change the oil a little more often than recommended.
    Get new tires before the wear bars start to show.
    Put in some fresh gas before you think it really needs it.

    To each his own.
     
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  10. walterm

    walterm Active Member

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    And I've seen references before when this quesiton has been raised that the car has enough smarts to run the gas engine when it's determined that it's gone long enough without running it/using up some gas. Exactly how long that is I don't know.
     
  11. MarkP.

    MarkP. New Member

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    Thanks for some replies.
    I failed to mention that one Toyota service guy mentioned that he would run the gas engine weekly, another wasn't sure but would use the gas engine more than i was doing. So this left me confused and not really trusting their replies.

    Replies to my questions were mostly about avoiding stale gas in the tank. Are there other concerns of components not being used often enough that warrant using the gas engine from time to time even when not needed?
     
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  12. bisco

    bisco cookie crumbler

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    you're asking for more opinions. no one at the toyota dealerships or here at priuschat knows anything about the prime engine running requirements.
    the engineers who designed it do, and everything you need to know is in the o/m. or not.
     
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