Is stale gas a problem?

How LONG do you figure it will be before you need gas.......that is, down to half a tank ?
In this discussion, time is more important than mileage.

No advantage to premium gas unless it is also ethanol free. Then an assumed slight advantage.

I would lean toward the 6 months theory.

 

i only buy a couple gallons at a time. i never considered condensation, is that a problem in modern fuel systems?

 

In general, no.
If you live where the spring and fall sees WIDE swings in the temperature over a short period of time......then maybe.

There is NO good reason to top up the tank with only a couple of gallons at a time under normal circumstances.

 

Several years ago I had a good conversation with a long-time friend of mine who was working as a chemical engineer in Edmonton regarding this topic. Here are the highlights I recall:

- Gasoline/Petrol oxidization is one of the biggest issues. As long the vehicle has no evap related codes then there are no detectable leaks in the system. Oxidization worsens when leaks are present even when they are too small to be detected and still within the design tolerances of your vehicle's evap system! So the advice is to add stabilizer to the fuel in the tank at least once a year if and only if, you do not add a good amount of fresh fuel at all. Toyota's recommendation (see user's manual or previous posts) is very sound on this account.
- Condensation and moisture, in general, is another big issue too. Temp cycling can promote condensation which is not ideal. This may also be worsened by the presence of ethanol in the fuel and the various percentages one is likely to find in North America. Let's say the concern is highest with the higher percentages of ethanol.
- It appears Gas/Petrol may experience some stratification when left still in a sealed container for extended periods of time. I suspect the constant physical agitation of the fuel on board of a PHEV driven primarily in EV mode is a strong mitigator for this concern. This is why I take the claims of "fuel aging" with some skepticism unless they include meaningful specifics.


Anyhow... in my particular case, I still have the dealer gas in the tank 1.5 years after delivery, a little over 10k miles and tank currently 1/3 full.
I added one bottle of stabilizer just before the 2018 winter arrived. Will do so again in October or November this year unless I add fresh fuel before then.


Cheers

 

I agree with your friend. Gas sitting in a plastic jug with a vent will have problems eventually. But a modern car's tank is well sealed and the Prius tank is pressurized, too.

As for the length of time you've been on the original tank? Just WOW!!! I got mine in early March this year. If not for a big 6,000+ mile road trip in May, I'd still be on the second tank. I take too many trips beyond battery range to stretch a tank that far. Current tank is almost to 2,500 miles. But I may decide to fill it tomorrow. I'm at 1/8 and need to make a fairly long drive Thursday to pick up friends at the airport.

 

I have two cars that only get fresh gas every two years when they are due for pollution inspection and have never had any problem with them starting.
They do get started occasionally and sometimes I remember to put fuel stabilizer in them. I have too many cars and can't drive them enough and don't recommend treating a car this way.
Water in your gas from condensation ended with modern fuel systems and most tanks are plastic today so only the air that is in the tank can have moisture to cause a problem. Don't over think it, put some gas in it and run it occasionally and you will be fine.

 

I used to run Ethanol fuel stabilizer, but NOT anymore.....

I switched over to real gasoline (E0) many months ago, I run it this way for all of my local driving because this gas just sits in the tank and barley gets used.

When I'm planning a trip I switch back over to cheap 10% Ethanol gasoline (E10), then with a little strategy I come back home from my long trip with virtually an empty tank. This way when I arrive home I can fill up with a fresh ~1/2 tank of Ethanol free gasoline and re-start my months and months of local driving knowing there's no Ethanol in my tank.


Rob43

 

Less gas in the tank = less weight, so faster acceleration and better efficiency. Although I haven't noticed any difference.

 

What exactly do you think is good about letting it STAY that low on gas ?
I think nothing.

 

Imagine that !!

 

If he is that successful at using the car almost entirely as a BEV, then why exactly would it matter what level he keeps his gas tank?

I can think of no good reason why it is either good or bad. Well, besides the fact that in the event of a collision-induced fire, a lower fuel tank will produce a smaller inferno.

 

The low fuel light will be on for a long time and the fuel sensor will be over used

 

That's really impressive.
And that's what I don't think Toyota communicates enough IS possible with a Prius Prime. Of course usage habits vary. But the fact that you can reach that type of SUPER fuel economy is something that I don't think the general public understands.

 

It's not really a matter of fuel economy, since the indicated or calculated mpg only accounts for gasoline usage and not for the energy provided from the wall socket. It is a very efficient vehicle but you have to include all energy costs (and usage) in the assessment.

 

A lot of speculation is involved.......ie guessing.
A large "air" pocket in the tank is more likely to exchange more air with the atmosphere, possibly resulting in more water in the gas.

Then....stuff happens.
What if there is a MASSIVE storm that cuts the power for weeks.
Living in Florida, this is a real concern and I'd prefer to have a full tank when/if something like that happens.
Things can happen on a smaller scale that might limit your access to fuel too.

Then there are things like a personal tragedy occurring and you taking off on an unexpected road trip when you aren't thinking exactly straight and running out of gas on the way.

I guess it is a personal choice......but I see no practical reason for leaving it low like that.
And several possible reasons for NOT doing that.

 

I leave the tank low when I'm around town so I don't haul a tank of fuel around for a few months. At start of a road trip I fill up and hit the road.

If a massive storm is headed our way (these are generally predicted well in advance) the option is there to fill the tank.

I don't expect it would be easy to run out of gas on a sudden road trip. The car starts warning you about fuel at least 75 miles from empty and even offers to find a gas station.

 

That is a great point.
An empty tank 'breathes', just like caves.
Much more air is exchanged at each and every barometric change, bringing in a new batch of humidity with each high swing.
And alcohol absorbs that humidity.

Could be bad, unless you live in Las Vegas where they always say, "But it's a dry heat!".

It's better to tote around a tank of gas. It's more weight but you'll never be able to measure the fuel economy differences.