How often should i run the gas engine

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.

 

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.

 

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.

 

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.

 

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 ??

 

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.

 

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.

 

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.

 

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.

 

I've found the engine coming on even in EV mode when it's really cold, even with more than adequate juice in the battery and air conditioning off. That said, I personally put about 3 miles on the hybrid in my commute daily even though I could do the whole drive on battery. I figure the EV is less efficient at highway speed so the 3 or so miles of my round trip commute I'm on freeway I use hybrid. Rest of the time (surface streets 50 mph limit) I do EV. That uses a couple gallons of gas a month while doing 90+% electric. That's just what I do.

 

^ Well even with plenty of EV miles left the ICE comes on at 84 MPH and above, if you floor it (sometimes depending on speed) and often when you use the A/C or defroster, you can hear it kick on especially when it’s recently been started.

 

@markp
Don't worry about it ! If you decide to take a drive just to use up gas in the tank, that is OK.
Many of us Prime owners and @bisco with his PiP only put a few gals in the tank when refueling, if we're not using the gas engine very much for months at a time.
I use non ethanol gas too, since every time I put ethanol gas in the tank I can smell (what smells to me like home heating oil ) from the gas station pumps (all year). Some gas stations around these parts have a stronger home heating oil kind of smell than others, but they all seem to have it, except the stations that only sell non ethanol gas. ( sorry for the run on, just one of my pet peves about gas).

If it were my Prime, I'd just wait, or go for a leisurely drive to use an 1/8 of a tank, might take 200 miles where you're from. Than just keep the tank at 3/8 to a 1/2 and you'll be able to add more gas anytime you want.
And it doesn't have to be 5 gals of gas every time you gas up, especially if you're using non-ethanol. Than run the gas engine whenever you want, without worrying about how often you need to run it. The only time I'd run the engine when the Prime didn't start if automatically, is before changing the oil, or to check it if I noticed something unusual happening while driving ie: messages on the MID (Multi Informational Display) screen.

 

Think DIESEL fuel.
Often stations or individual islands that have a nozzle for E0, do NOT have one for diesel.
Just a tiny bit of spilled diesel will smell for a LONG time.

 

I don't have a Prime but very interested in how y'all manage the gas possibly going stale and also ensuring the engine gets sufficiently used.
I've had a 4X4 Tundra for years and for maintenance is important because we have stuff that can go months and months (even years) without use, so we're told to engage our 4x4 system (4-high and 4-low) at least once a month for at least 10-minutes to get all the transaxles and differentials moving and parts freshly lubricated. I do mine the first day of every month on either gravel or icy roads or in a straight line. (You don't want to engage 4x4 on a dry road while turning...can break stuff.)
Gas in a gascan can go stale, even though it's not getting any outside air, and a gas stabilizer additive can help but I'd be worried about the stabilizer doing something to my sensitive injectors and other engine parts.
Maybe only keeping a couple gallons of fuel in her and ensuring you drive enough monthly to burn it off which would, also, help keep the engine lubricated sufficiently.

 

So far, I don't recall anyone here getting in trouble yet from following the Owner's Manual. And some do use hardly any gasoline in a full year. From the 2022 Prime Owner's Manual:




The whole PHEV industry designed their sealed tanks to keep fuel good for a year (though original PiP Owner's Manual called for just 6 months):

Autoblog: How desiging the Chevy Volt's sealed gas tank brought automakers, CARB together

"... but now we've got the scoop on the gas tank used to keep liquid fuel in the Volt from evaporating or going stale for up to a year."

 

For a while, when Gen 4 and Prime were new, there were several threads about people getting gas splashed back on them from the anti-vapor collar on pump nozzles hitting the switch that told the car you had closed the fuel door. (Later models put a guard over the button.) That would close the valve that seals these tanks and the only place then for the gas to go was on your pants and shoes. (So much for evaporation prevention!!!) These tanks are very well sealed and I, too, have never heard of gas going bad in one of them. Aside from vacation trips, I fuel my Prime with ethanol gas about every three months. Last time, I went four months and 3,500+ miles and still had a quarter tank left.