Featured 2024 Prius Prime- any issues with gas getting old?

From my experience with small engines, gas any older than 6-months tends to start breaking down and doing bad stuff to things. (Like forming a nasty gum residue.)

You also need to take care of that internal combustion engine (ICE). It's not good for any engine not to be run and lubricated like designed. Maybe switch to hybrid or sport mode a few days a week to give everything a workout and burn some of that old gas off? In the long run, the money you spend for gas will pale in comparison to needing the fuel lines flushed to remove the gum or for engine work.

I have 4x4 in my Tundra but I don't use it all that much...just during the worst winter months. To ensure the front axle gets lubrication, I'll engage the 4x4 system at least once a month, all year long. Many mechanics recommend this as they see 4x4 front axle problems by folks who rarely use them...and when they DO engage them, find them non-operative needing repairs.

 

regular gas is OK if you're going to use it in a month or two.
No one says you have to fill the tank every time you stop at a station either.
If you run mostly EV than there are a couple of things you might want to think about when gassing up.
How much gas are you going to need for the next month or two?
Do I really want winter blend gas in my tank during spring and summer time?
Is it worth it to me to spend a little more for non-ethanol gas that might be cleaner than the regular gas most everyone pumps on a weekly basis?

link to a list of canadian and us stations that sell non-ethanol gasoline.
Pure-gas.org - ethanol-free gasoline in the U.S. and Canada

 

As Tideland has mentioned, previous versions of Plugin Prius says in owner's manual that gas is good for a year, but in truth the experts say 6 months.

Whenever I see a plugin Prius at a Gas station I asked them the last time they filled up the tank. Usually the answer is a "few months" but some say "almost a year."

Old gas is going to cause your engine to run rough and not much else. But over time it could cause damage. Of greater concern is ethanol in gas, which attracts water, as well as builds up lamination damage in the engine.

If you want to do all you can to protect your new Prius I'd reccomend only buying gas without Ethanol in it. It has 2% more BTU too! But it's hard to find thanks to the corn lobby trying to sell corn as ethanol, which pollutes more to produce even if ethanol additives do help gasoline burn slightly cleaner. Here's a map to find out where to buy non-ethanol gas: https://www.pure-gas.org/maps

 

For emissions, a car's fuel tank is much better sealed than what gas for a lawn mower is stored in. That means the degradation of the gas is much slower from the lack of air reaching the fuel. A PHEV's tank might even be better sealed. Unless you are at 100% EV use, you shouldn't worry about the gas. Can't say for sure about the Prius Prime, but other PHEVs do track the last time fuel was added, and will give a warning when it has been to long to add fresh fuel. Some will even use the engine to burn off old fuel.

Octane rating doesn't make a difference to fuel life in a car's tanks. Stick with regular.

Ethanol free gas does have a longer shelf life than E10, but the engine and fuel system is designed for some ethanol. Then most ethanol free gas is non-oxygenated, which has higher CO and soot emissions. Plus it might mean more carbon deposits in the engine; ethanol is a good engine cleaner.

 

I’m treating the gas in the tank as if it has a one to two month timer and then refilling on a longer interval only if I absolutely need to. Even if it’s 6 months until it actually goes bad, there’s no need to push it. It’s not a true EV. 6-12 fill-ups per year is fine if I’m driving it that much.

Even if the gas doesn’t go bad, the gas engine should be run on medium or longer runs occasionally for oil health. Short runs where gas only comes on for the minimum amount of time are generally not healthy. Some open revving under load and/or constant heat on a highway can avoid this issue.

 

I skip a charge session from time to time to get some ICE use more or less every week. Tons of EV driving did spoil me and I feel odd when ICE kicks in.

Take up hiking and go on longer trips Big benefit of the Prime is you can go into the middle of nowhere and still get out unlike my hiking buddy with a Tesla who has to pull out his navigation charts and a sextant to make sure he makes it home

With my local gas and electricity pricing, the difference is couple of cents per mile, so it's not going to make a dent, but the engine does need to be used.

 

Emphasizing Approximate Pseudonym's point here...

It's not a bad idea to take a longer trip(30min or more) at higher speeds to get the engine up to full operating temp for at least 15min once a month or so just to cook out any accumulated moisture in the oil, make sure all the internal surfaces have a fresh coating of oil, and include a few sustained hard accelerations to break any carbon deposits free. Once or twice a month is all it needs, but that should also use enough gas over the course of six months to require a fill-up or two and prevent any stale gas. Some even say to do this once a week, but I think every other week should be fine.


As I type this, I'm prepping for one of these trips myself. I live in a community of less than 10k people and less than 10 square miles(25 square km). That means almost all of my daily trips are less than two miles(often less than one). Every week or two I have to make up a reason to drive to one of the two closest cities(30mi & 50mi) mostly as an excuse to get some heat and miles on the car.

 

I had to laugh when AMD at TheCarCareNut just happened to drop a video today and it's all about the RAV4 Prime, including its care and feeding. He pretty much says the same thing I just said above, which makes sense since I get so much of my info from his other videos. lol

Most of the important maintenance stuff starts at 17:54. (this all applies to the Prius Prime as well since they use the same system)
- Use HV mode one day a week to keep the ICE healthy
- Shoot for one tank of gas no more than every three months
- The programming to auto run the ICE after six months of no use is basically worthless since all it does is run one warm-up cycle; using up a few ounces of fuel from the tank doesn't magically make the remaining gallons of old fuel fresh again
- Oil changes at 6m/5000mi are just as important(maybe more so) on a PHEV no matter how much the ICE is used
- There's a heat pump service at 80k miles to check refrigerant level due to the system also being used for battery cooling

 

There's a youtube by a Toyota mechanic claiming that a prius prime owner didn't start the gas engine for 18 months and the engine is ruined because of corrosion. Page 86 of the owners' manual is oddly specific about this matter - 5.3 gallons every year. Turns out that's exactly half the tank. Personally I wouldn't even push it that far. 3 months is as long as I like to go with gas without stabilizers.

What I've noticed is that the car defaults to EV so it'll almost never run the engine. Even in Auto HV/EV mode it won't run the engine. You need to manually put it into HV mode for it to run like a normal prius. I plan to do that once a week to slowly burn the fuel in the tank.

For Plug-in Hybrid Electric Vehicles,
fuel may remain in the tank
for a long time and undergo
changes in quality depending
on the how the vehicle is used.
Refuel at least 5.3 gal. (20 L,
4.4 Imp.gal.) of fuel every 12
months (refuel a total of at least
5.3 gal. [20 L, 4.4 Imp.gal.] over
a 12-month period), as this may
affect components of the fuel
system or the gasoline engine.​

 

Ecu isn't programmed to run the engine after a few months automatically?

 

Yes, but not enough to use any significant amount of gas. After 6 months, it will run the engine for maybe a couple minutes.

 

Sounds like an engine maintenance mode. The Volt had an additional fuel maintenance mode to burn off more fuel. PHEVs were a new concept then, and GM may have been overly cautious for the sake of avoiding issues. I expected that to change with the gathering of field data from the cars, but I suspect Toyota hasn't changed the software much from the PiP.

IIRC, that maintenance cycle was more frequent than you report here, but the PHEV design with 4.4kWh battery meant the engine was firing up quite often compared to the Prime. There wasn't any reports of bad gas in the gen4 Prime, but the gen5's increased range does increase the risk of it, if there is no fuel maintenance mode for those few cars running almost entirely on EV.

 

I'm going off of what TheCarCareNut said in his recent video on the RAV4 Prime. And I agree with you that the Prius Prime/Rav4 Prime behavior sounds more like engine maintenance rather than fuel maintenance.

 

With 50 miles use a week, not much to work with. Purposely drive one or two days of the week in hybrid mode, say Mondays and Fridays? Shouldn’t break the bank.

I shouldn’t talk: our ‘10 hit 100k kms Christmas Eve, and we’re currently around 100,650.

keep an eye on your 12 volt too.

 

Well, personally when i know that i'm not going to use gas for a long while (summer), i put some fuel stabilizer in the tank with some premium fuel as Octane level tend to go down a bit as the fuel ages.. don't ask me why however.

During winter, it's 87 all the way!

 

Octane drops cause of evaporation and oxidation. It can drop alot in a lawn mower during the off season, which is probably why those recommend higher octanes.

Car gas tanks are better sealed. Fumes don't get out, and the air in them isn't changing over. The fuel simply doesn't degrade when compared to what is in a plastic gas can.

 

I read somewhere that at about six months the car will know that the fuel is getting old (timer I guess) and only run on petrol (gas) until most is gone. I know this is the case with Volvo PHEVs.