Do I NEED to fill up every so often?

it's not a matter of filling up, but using the gas that you have. i would try to run through a tank every year or less, but don't let it go below the out of gas light. there are still a couple gallons left when you get the warning.
and you don't have to fill it if you're not using much gas. half a tank is fine.

 

Gasoline starts to break down after a few months. Our local dealership offers a free service to swap out your old stale gas for fresh gas, once a year.

 

You are undermining the world economy. Because of you, the price of oil is falling. Aren't you ashamed? Get to the gas station now!

 

Sorry, that's false - just driving down the road is enough to agitate and mix the fuel. Modern car fuel systems are sealed up pretty tight; though old fuel in the tank is an issue.
IMHO; you should be exercising the engine every two weeks or at least once a month for 15 minutes minimum. This will lube the mechanical parts and burn out all the accumulated moisture and contaminates in your engine & oil. Depending on how long it takes you to get through a tank of gas; I'd also think about putting fuel stabilizer in there. I do that with my lawn mower gas because it takes me a good 9 months to get through 2.5 gallons.
Or you can trade it in for a BEV and not deal with the ICE at all.....

 

Plan a long drive to a gas station that sells no-ethanol gasoline: Pure-gas.org - ethanol-free gasoline in the U.S. and Canada

Once you've used up all the existing gas and have ethanol-free gasoline in the tank you'll be able to maximize how long you go without buying new gas. As in ethanol attracts moisture and makes gas go bad faster than gas without ethanol.

 

Maybe just drive it like a hybrid regularly, say one day a week. It’ll cycle the gas more, and benefit the engine.

 

I know you just bought it, but do you need a hybrid? A used short range (under 150 miles) EV should be relatively cheap. Do you need a car at all? At 3 minutes I'd walk or bike to work.

 

depends on the weather, but you want the engine to complete the warm up cycle and shut off.
otoh, 3 minutes creates a lot of pollution. i'd be more inclined to take a 20 mile drive once a week with no wall charge, maybe 50/50 highway and back roads

 

I think Bisco's advice is for the earliest version of plugin Prius that Bisco used to have and doesn't apply to the newer ones, which don't have an ICE warm up cycle until the battery charge is depleted enough to justify it.

 

It's good to have a full engine warm-up, regularly. My wife and I are both retired,, fixed income, not using our '10 that much. We do occasionally need to make a cross-town drive, run out to the airport, stuff like that. We try to do most shopping at lnearby, stores, on foot (we're lucky to be quite close to a few "corner stores" and a Walmart), and then when we're obliged to do a long drive, and it's doable, we'll do heavy-item, stock-up shopping on the same day.

When your usage is low you want to strategize, to keep the engine happy.

Also consider a charger regiment for the 12 volt battery.

 

I thought you had an engine block heater to eliminate the need for a warm up?

 

Yes, use that before cold-starts virtually all the time. But it it doesn't result in a totally warmed up engine; raises coolant temp 20~30C above ambient..

 

Drives that short could be worse than just using electric.Yeah, you'll use up gas, but the oil will never warm up enough to dry out, with more water from combustion getting added each time the engine ran.

Previous PHEVs kept track of when gas was last added and used. At some point, the car will alert the owner to add fresh gas, or it will go into hybrid mode only to start using up the old fuel. You might of gotten it, if you drove all EV since you got the car. The manual should have details on this. The tank is well sealed, so age related break down is far slower than that of gas in a lawnmower. I wouldn't worry about that.

From now on, I'd use hybrid mode for trips over 10 minutes long to use up the fuel. and then add only the amount needed instead of filling up. It usually takes 3 gallons to reset the 'old gas' timer.

From reports here, I'd be more concerned with the 12Vbattery than the gas with such short trips.

With such usage, it would be worth looking into your state's low speed vehicle regulations. A street legal EV golf cart can work for the commute, while keeping the old gasser for trips.

 

running it in charge mode is fine, you will burn the gas up faster

 

Driving that Prime in all-electric mode is fun. I did that for about 3 weeks when I bought mine (2017 Pime) last year. Then one day, I did a calculation to see how much I was saving by driving around in all EV mode and here is what I got:

I put in about 6 KWh of charge and pay $0.20 per KWh (in FL). But the charger is not 100% efficient (it uses about 10% more than what it actually puts in) and I actually put in a little over 6 KWh (like around 6.3 when fully empty). So, I came up that $1.50 is a good estimate for the amount required to fully charge my car. I get 25 EV miles (no A/C and EV driving in mind.) Doubling that would give me a comparable number to MPG. So, $3 worth of charge for 50 miles of EV driving.

Well, I pay around $3 (most of the time under) per gallon of regular gas here in central Florida since January. And my Hybrid MPG is around 65 miles per gallon. I have been driving Pruis since 2017 (my first Prius was a non-plug-in hybrid), and I learned all the tricks to max up the MPG.

Well, I realized my car is more efficient when I drive it on hybrid mode and I switched to driving it in Hybrid mode since January. But this doesn't mean, I don't use the battery. I use about 5 KWh of charge per week. Combined with the gas, I get around 70-75 MPG and a tank of gas gets me around for 700 city miles (I pump around 9.5 to 10 gallons into an empty tank). It is crazy efficient, and I absolutely love it.

The traction battery is very small in Gen4 Prime. It doesn't last long. And if you keep charging and only use the traction battery for EV driving, you may eventually start seeing that your battery will slowly degrade. Prius Prime is designed as a hybrid vehicle. Yes, they include a traction battery with some capacity to get us around, but I don't think the purpose of this vehicle was to let us drive it in all EV all the time. It cannot be very efficient this way. You carry that gas engine with you everywhere first of all. It is not there to carry around. You need to use it.

If the purpose is to drive around in EV mode all the time, one should think about an EV vehicle instead of a hybrid one.

With this said, your short daily commute of 3 miles is very ideal for using your vehicle in all EV mode (especially if you have solar panel on your roof or you have a way to charge it for free). There is nothing wrong with that. You don't want to run your gas engine for a few-mile of drive. It is not smart. But when it is time to travel or you need to drive it farther than (say 10-15 miles), you should gladly use the hybrid mode. That gas engine needs to run time to time. And your car is just as (if not more) efficient in the hybrid mode.