Shogunade

Is it bad to keep gas in the tank for a while? This is gonna be a weekend car. Any reason not to fill her up?

shrimp money

I think if you're not at least cycling it out every 3 months, don't bother filling it up all the way.

Staffie Guy

I would not keep gas for more than 2 months. If you have older gas in the car, add a fuel addition for protection and fill in with new gas.

detansinn

If you are keeping your tank less than full, condensation becomes an issue. So, there are issues either way.
The key is to go on real drives. Typically, when I am starting the weekend car, I am going on at least a 2hr drive. Full heat cycle. Battery is certainly charged up. Good exercise for the vehicle.

audi4t

I have a BMW at my vacation home the car is not used or started January thru’ June.

I leave it in the garage with whatever amount of gas is in the tank - most times NOT full. I don’t add any stabilizer.

I have been doing this since 2014.

I leave the car battery connected to a trickle charger.

Every time I return in the summer the car starts and runs fine.

Tupper

I think that the fear of gas “going bad” keeps companies that make Sta-bil in business.

But instead of testing the limits, most people will just buy and pour the Sta-bil in for piece of mind.

I imagine that you’re totally fine for up to 3 months. Maybe a bit longer. But I have never used Sta-bil and I keep my car mostly undriven in the winter without issue

ipse dixit

I think a lot of this depends on the climate (temperature and humidity) where your car is stored or parked.

detansinn

Excellent video on fuel stabilizers…

Radiationman

Exactly... How many military members go on deployment for 60 to 180 days if not a year and leave their car parked with no issues...

There's no denying that gas does "go bad" at some point but you're probably fine for at least 6 months assuming that there is some activity with the car.

That said - do what give you piece of mind. If you're concerned - then dump some Sta-bil in the tank so you don't stress over it.

Richard_Wallace

There have been dozens of tests over the last 30 years on this: but to summarize some of the more recent (modern gas and modern cars).

A modern car with pure gasoline starts to oxidize in about 6 months. Gasoline containing 10% ethanol will start to oxidize more quickly and averages 3 months before the oxidation process starts. The higher the ethanol content, the faster it will start to oxidize.

Doesn't mean that the car won't run, but will start to oxidize and gain higher moisture content (AKA water).

Diesel gas is around 1 year and oxidizes much slower. (I have had tractors sit for 3-4 years and still started with old diesel fuel..).

The use of products like Stabile will help maintain your gas (slow down oxidation) from around 1-2 years (again depending on gas type, amount of ethanol, etc.).

There are also some that believe that if you are going to store a car for a long period of time (meaning 3-6 months or more) to store it with a full tank. This is actually not the way to do it, while you think it would give less room for oxygen, the oxidation process still happens (as these are not air tight systems). It is best to store it lower on fuel (meaning less than 1/2 tank. That way when you are ready to drive it, you fill up with mostly fresh fuel mixed with less partially oxidized fuel... Really not a problem unless you are storing for more than 6 months IMO.

On the flip side if you have a very high end storage gas can - the 5 gallon type (I keep 2 of these full at all times) - they are air tight and if kept full, will keep pure gas nearly 1 year before severe oxidation. I use these to power my UTV''s, mowers, gas tools, etc. While I typically will easily go through these in just a few months, sometimes they do sit a bit longer - so good to keep around as a backup.

ipse dixit

This is one of those typical situations where “it never hurts to do it, but it might hurt a lot if you don’t”.

IPA1

Rec 90 fuel is readily available with no ethanol. I believe, someone correct me if I'm not, that aviation gas is also ethanol free. These do much better than typical street (ethanol) fuels for longevity. That said when ethanol fuels go bad, they really go bad and create little orange ***** of snot that reak havoc on everything. I've cleaned too many marine tanks, filters, etc., due to broken down and phase separated fuel. Stabil or other treatments are well worth the cost for some peace of mind. The oxidation / breakdown process is mostly independent of fuel level. Condensation is not and it is also a real issue. Although I do not plan to store my car for long periods, it I were, I would run Rec 90, Avgas 100 or similar for several tanks prior to parking. Keep the lower octane in mind if appropriate. Bad fuel makes for a bad day.

22992

I go 1/4 tank before putting the car away and use stabil 360. First drive in spring is to fill it up with fresh gas. Stabil is so cheap, and I use it in everything. Riding mowers, generator, weed wackers etc. everything starts 1st pull after winter.

wingless

Fuel stabilizer is fine, but the issue is ethanol.

The ethanol WILL separate from the gasoline regardless of the prior addition of fuel stabilizer.

Gasoline stations near boat launch ramps will market / sell ethanol-free premium gasoline. It is 100% fine to keep ethanol-free premium gasoline in the fuel tank for extended period. It is better to add fuel stabilizer with the gasoline, but that is not required.

icanthelpit

Is this your first car? The thing you should really be concerned about is the air in your tires getting old.