Is fuel stabilizer necessary?

A month? I personally figure I can go a year on a tank.
Since gasoline is generally stable for a year I don't think I will use a stabilizer.
If you go through a tank a month and stick with a reputable fuel (aka TopTier)
I think you can avoid using it as well.
I am sure there are a lot of opinions as to whether a stabilizer is safe in the Prius.
I defer that to those more versed than I.

 

Gasoline goes bad because more volatile fractions evaporate off, and the rest starts oxidizing. So octane drops, and gums can start forming. Which is why it isn't recommended to save gas for the lawnmower until next season.

But that gas is usually stored in a cheap plastic can. The fuel tanks of modern cars are better sealed by far, which keeps the gas fresh. It won't keep forever, but the manufacturers of PHEVs have the system set up to burn off fuel it deems to be too old. So stablizer isn't needed.

 

+1.

 

pip manual says 6 months is fine

 

Indirectly, that sounds right. I don't see how the pressurization itself helps, but the sealing necessary to keep it pressurized would certainly put a halt or sharp limit to the evaporation and oxidation that cause problems.

 

If you have to push a button and then wait for the car to tell you it's ready to refill, the tank is pressurized.

 

Has anyone seen a reminder to add gas? I drove mine for a year and never got a reminder.

 

An improperly fitting gas cap will cause the check engine light to come on for most cars. Even happened on my 2000 Ranger.

 

My basic understanding of the physics is that the liquid will continue evaporating until its partial pressure within the gas mixture above matches the vapor pressure of the liquid. (For a complex mixture such as gasoline, this makes for a complex situation, each chemical having its own separate balance point and evaporation rate.) Since the outside atmosphere contains very little of this stuff, its partial pressure there is near zero, so the only way to get this partial/vapor pressure match on top the liquid and halt further evaporation is to seal the container.

Overall mixture pressure inside the container isn't relevant to the evaporation, except to prevent boiling. As long as it is well sealed, it could be under pressure, some minor vacuum, or neutral, they all can work. But container pressurization does allow the car to easily check for leak rate and report a problem to the driver.

Maybe someone else can further illuminate the situation. Hopefully not with an spark of ignition ...

I believe US rules have tightened since then, pushing for improved solutions. The Gen2 bladder was one of the attempted improvements.

 

Where exactly do you get that "information" ? Reference please.
And I suspect that almost nobody questions the safety of properly used stabilizer.
The debate will be whether or not it is NEEDED.

Personally I would be a bit nervous if the fuel isn't used up or "refreshed" withing 90 days.
Certainly no problem in just 30 days.

 

How long gasoline remains good depends on several factors. The sealed gas tank is important. That keeps volatile fractions from evaporating off, and keeps atmospheric moisture away. The actual chemical composition of the gas we buy any specific day can vary. Another point is how good is good, and how bad is bad.

Gasoline quality is lower after about 30 days. 90 days max without a stabilizer is probably a good rule of thumb, and one year with a stabilizer is a reasonable limit. And, it all depends--some engines are finicky about the quality of the fuel, and some will run with almost anything. How to Keep Good Gas From Going Bad This Winter 2018 in 3 Easy Steps

So, if your Prime is running fine the way you're doing things, great. If you never need to buy gas, I'd use a stabilizer. It's cheap. The car will be ready for you for the day there's a power failure and you can't recharge. Getting the fuel system drained and cleaned is expensive. Or, periodically switch to HV, use some gasoline, and top it off with new gas.

 

Just fill up the amount you would end up using. Gas stations are abundant. Don't fill up over 50% just carrying extra weight TBH

Posted via the PriusChat mobile app.

 

I drove December 2017 to December 2018 on one tank a gas and the car never warned me to add fresh gas.

 

The longest interval for gas fill-up on my PRIME has been 2 mo. I usually get the tank filled at least once a month, and in winter, when EV range is short and I don't charge as often, I refill every 2 weeks. No need for stabilizer for my PRIME. That said, I have kept 10% ethanol gas in my lawn mower over winter many, many times usually without any noticeable problem. I guess I am just lucky.

 

But did you ever notice the gas engine running sometimes when it really didn't NEED to ?
My guess is that it uses up some gas automatically and relies upon the driver to notice that it is running low.

But then based on some of the posts here, that assumption might be a bit optimistic.

 

Like most people, do you do nothing in terms of prepping the mower for winter?
I'll run the fuel out, and then add some rubbing alcohol to the tank at the start of next season to get any water in the carb bowl out.