Can gas go stale in the 2020 Prius Prime hybrid plugin?

1. Yes, but not "use up". It just fires up the engine if the gas sit un-refueled for ~6 months IIRC.
2. It will never flush "all" of the gas, unless you go on HV mode until the tank is dead empty. The gas empty light will come on at about 2 gal still remaining in the tank. Toyota recommends adding at least half a tank every 12 mo. You do not need to flush out all the fuel as long as you are adding at least a half tank (5.3 gal) every 12 mo. If you think you are going to go longer than say 6 mo without refueling, some people add gas stabilizer in the tank. Personally, I think it is cheaper to just burn the gas every once in a while and if you know you don't use the gas much, just less than half tank of gas at your next refuel.
3. Never, on it's own. See answer above.

In Canada, when it gets cold enough, the gas engine will fire up more frequently to provide heat. If you are regularly driving above EV range, I would not worry about the fuel going to stale. I refuel my PRIME much less now since I do very little driving, but still it is shorter than 12 mo Toyota recommends.

 

The Service Manager at my nearest Toyota dealership told me that one of their other customers drives his Prius exclusively on EV. As a result it never consumes its gasoline. He brings his Prius in once a year and the service department swaps out the old gas for fresh gas.

Personally if it were me, once every summer I would take my wife on a 100-mile trip somewhere. Just to ensure that I run the tank down to one-bar and refill it.

 

This has been discussed extensively on here many times.
A little searching might eliminate the necessity for yet another repetition.

And.....the guy who paid a shop to "swap out" his old gas:
How stupid.
Just run the engine.

 

#1 sounds like an engine maintenance mode. The car fires up the engine every once in awhile to ensure things still work and to circulate fluids.

Other PHEVs have a fuel maintenance mode for when no new gas has been added in some time. In theory, the Prime has one, but no one has reported having it happen. For the Volt, it was something like a year without adding fuel.

A car fuel system isn't a gas can used to fuel a lawnmower. It is far better sealed against vapors leaving, and air coming in, and that is what leads to gas going 'stale'. If you are already using gas with just having the car a week, you will likely need to add fresh gas before any fuel maintenance mode. If you do find you aren't using the engine, leave the tank half empty, then you can add fresh fuel as soon as the car enters a fuel maintenance mode. The Volt gave a warning it was needed before actually turning on the engine.

 

Fuel systems on PHEVs are far better sealed than on any other cars on the market, so their fuel goes stale slower. GM and the other car makers and CARB worked together to design fuels systems for these vehicles:

"... 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. "

How designing the Chevy Volt's sealed gas tank brought automakers, CARB together | Autoblog

 

I believe that it is incorrect to state that the 2020 Prime will fire up the engine if the gas sits un-refueled for 6 months. The manual just says a warning will be displayed if the car thinks the gas my be getting stale, right?

 

At one bar on the fuel gauge there's 2 or 3 gallons of gas still in the tank.
Even with know 0 bars on the gauge and 9 miles left on the DTE odometer there is still a gallon left in our cars 10.5 gallon tank,
Closer to a 400 mile trip to get a full tank down to 1 bar on the gauge.

 

Depending on what you find your actual usage to be in a month or two, you could refill with a month or two's usage of fresh gas each time, once you have run the current tank. Based on Toyota's recommendation of running at least a half-tank in an year, which amounts to running about a mile a day on gas, I try to run the Engine on "Charge Mode" for 5-7 miles (15 mins in city driving) every Monday. This not only puts the gas to good use by adding to the battery charge but also makes the engine run hot enough to expel any moisture in the system, besides assuring a working ICE, when you do in fact need it. If your gas usage comes to be too minimal, you could even try and use ethanol-free gas such as the "Recreational 90" at some Marathon stations, which is what I do, but do NOT use "marine" gas which might contain MTBE which isn't compatible with regular ethanol gas that might be in the tank already or might be used in the future.

 

how can there be only 9 miles left, if there is, "still a gallon left" ... unless you're hauling a loaded trailer in freezing cold weather.

yes - but the Volt will also come on periodically (maybe ~6weeks?) and run for roughly 5 to 7 miles, turning on your speed & temperature. But yes - gas tanks are sealed to stop gas from oxidation (turning into a sort of varnish) - even to the point if the gas cap seal is bad - cars will throw a code. The Volt manual says that once there's two gallons added (even if you still have over 1/2 tank) - the clock is reset, so to speak - resetting the yearly gas runout.
You can defeat the occasional 6 week cycle (for instance) by running in "hold" mode ... where the traction pack will maintain its present status - whether 20 or 90% full ... and let the car run as a hybrid. Especially handy below freezing temps - as the pack can warm more quickly off engine heat / coolant, as well as the cabin can be warmed off of the coolant - in stead of electricity ... and then it bypasses the occasional maintenance mode.
.

 

I'm just reporting the gauge readings at time of fillup. I don't pretend to understand how the Prime defines the estimates. I put 9.5 gals of gas in the tank while the DTE odom gauge was showing 9 miles left of HV range. The DTE changed after fillup to 495 estimated miles of HV range..
The next service area was 45 miles away, which was about the distance to my destination as well.
I probably could have made either the next service area or my destination without stopping for the fillup.
The other thing on my mind was what I would be hearing from the passenger as I'd already been told several times the gas low light was ON..
edit: The car also had 28 estimated EV miles which might have taken me 10? EV only miles at 75 mph.

 

Yeah, @Trollbait pointed out my confusion. It is the engine maintenance mode, and IIRC, it comes on a bit sooner than 6 months.

 

Interesting...

Essential COVID Protection for your Car + Electronics Accessories

 

Who is this guy? And what part of "Toyota" did he contact, someone at corporate, or just a mechanic at a local independent owned dealer that happens to sell Toyotas? He doesn't sufficiently identify the quality of his contact.

"If ever you are not driving your car enough to use a tank of gas in a month or two, you should add a fuel stabilizer to your gas tank to prevent the gas from going bad and eventually causing engine damage, as well as blockages in your car's fuel system.

... Since taking delivery of my new 2021 Toyota RAV4 Prime plug-in hybrid in August, I’ve mostly been driving using electricity, so recently I contacted Toyota for advice. They recommended that I add an additive called Sta-Bil to my gas tank:

...Sta-Bil 360 Protection is for vehicles that are driven occasionally. It will stabilize fuel for up to a year, ..."

Hmm. This product "will stabilize fuel for up to a year." Or choose to RTFM, go without any stabilizer, and possibly need to add fresh fuel in just 12 months, according to the official Toyota RAV4 Prime Owner's Manual:

page 91:


page 84-85:

 

Yeah that second paragraph makes a LOT* more sense. Doesn’t take a special trip though; just use the engine once in a while.

(Frying pan clangs against head...)

*Why burden the dealership with such malarkey, and a tankful of stale gas to dispose of; the guy is over the top OCD, lol.

 

...so the mechanic "disposes" of stale gasoline by dumping it into his pickup, adding some fresh gas, and delaying buying his next tankful.

 

Another thing you can do is google "non ethanol gas near me" and get your gas there. That will give you much longer time to use up the gas. Non ethanol gas lasts much longer and does not gum up. It is good for chain saws, snow blowers and lawn mowers too.

 

Hmmm. I kind of think a lot of people worry too much. I bought gas for my Prime twice in 2020 (March and August) and drove a bit over 8,000 miles which is roughly half of normal due in part to COVID but also other factors. I still have over a half tank left. Never any stale gas issues with 87 octane E10.

Had we taken my Prime to Ohio this fall rather than the wife's Trim 2 Prius, that scenario would have been very different.

If I was never running the ICE then I would take some measures which would absolutely not involve paying a dealer to dispose of the gas. As it is, I go beyond battery range roughly four times a month, so that gradually uses it up.

 

Yeah that is complete OCD. They’ve PAID for gas, and rather than use it they have someone siphon it out??

 

So, what symptom on PP are we expecting to see if the gas does indeed go stale? I know about the gummed up carburetor on a lawnmower, but can something similar happen on modern cars like PP without a carburetor?

BTW, I know I am not supposed to keep the gasoline in the tank of the lawnmower or snowblower at the end of the season, but I often do. E10 gas and a shot of Stabil have always worked and I have never had any problem starting the engine following season with obviously "stale" gas in the tank. If the engine is hard to start on the first pull, I just use engine starter spray, and once starts, subsequent starts are usually much easier.