Old Gas? How old?
 

Haven't driven the Mustang since March since we only used it to go to our favorite pool hall & back home. Tank full of 91 ovtane no alcohol fuel.

Started thinking about it..decided to burn off the old stuff. So, made a boring 150 miles round trip on I-5. Ran 4th quite a bit to burn more. Should have driven more, but got tired of it...so only 1/2 of a 16 gallon tank burned.

Actually, the car ran pretty good on 8 months old gas...good performance at full throttle, no pings heard. Maybe because the '08 Bullitt was the first Ford to read octane and deliver timing accordingly,,,car does and will run fine on 87 octane gasahol, but delivers more horsepower with higher octane. So, I pay the premium for the good stuff. Mine is an '09, by the way. Not much difference between the '08 and '09 Mustang Bullitts.

So, 10 miles from home added Sta-bil to treat the entire 16 gallons, topped off with 8.2 gallons of no alcohol 91 Octane. "Pure gas", it's called.

No problems to report, but this got me thinking...how long does it take for gas to go bad? How much more time does Sta-Bil give you? It's all guesses for me...

In a modern car with a well sealed gas tank inside a garage I'd think about 12 months is the maximum.
But if you ran that car regularly then you could extend this time by a lot.

In an older car stored outside not driven maybe less than 3 months. Inside a garage under a cover. Close to a modern car IMO.

Sounds like you're fine, burn it up. Do you have ethanol in your gas up there? That crap is a water attractant and a partially filled tank left for months can have water in it. Especially if it's been parked in the sun at all. You would've experienced sputtering already if your tank was contaminated, as water is heavier than gas and your pick up is at the bottom of the tank. I put a little ATF in my small engine tanks that don't get used within 2 months. Cheaper than preservative and works the same. Without it I've had to clean out varnish flakes in the tiny carburetor jets using a single wire from a scrub brush. I miss the good old red gas that smelled like gas.

When my 911 was down for my painfully slow suspension rehab, it sat for about two years- full tank no ethanol, no stabil, no problem.

Guy I know runs avgas in his car collection. He claims it is good for multiple years. So far, evidence supports this.

I ran no alcohol premium in my SC and 930. Both had periods of little to zero driving. I think the SC sat at least 8 months once and I had zero issues.

Now alcohol gas? Seems most lawn mowers crap out over winter.

Ive been hearing this for years. I fill up my mowers every winter with cheap gas and they fire right up in the spring. 8 years on the current push mower.

Avgas does have long term storage properties as many aircraft are pure hobby toys and only flown on perfect weather days which can be hard to align with days off or the time to fly for a $200 hamburger.

It does have some lead in it, so catalytic converters are not happy with it. And it is rather pricey like race fuel. Race gas has storage additives as well.

If I know I will have a long period of time of storage, I will throw in some Stabil as a cheap "belts and suspender" option. Pretty cheap insurance that is really easy to do.

Ethynol? Better drain that fuel system, it will trash it out. Trust me on that. LOL!!!!

back in the early 90s, my dad owned an '82 corvette that he loved. He was stationed in Spain, and put the car into storage near where I was going to college. I was supposed to go start it and drive it around inside the storage complex just to keep the fluids moving. I think my parents were gone about 3 years. By the time that he got back, the gas was definitely bad.

Apparently, the time is 1<3 years.

I think you're fine using non ethanol gas, that's all I burn in my cab, boat and yard tools. A little harder to find.

Definitely hard to find, and I pay a premium for it...luckily, a station that is exactly 10.2
miles from my home carries "pure" gas.

I start putting Stabil in my gas can in the fall and from that point until putting them away, mowers, chain saws, leaf blowers - everything gets Stabil in 93 octane 10% ethanol gas. I've never had a problem.

No Stabil in the old gas...I hadn't planned on the virus lockdowns. Yes, the current full tank, a roughly 50-50 mix of 8 months old "pure" gas and fresh "pure" gas has Stabil. Should be okay until I get back to a usual driving pattern. Hope so anyway.

I'm a big believer in using stabil. I have several cars stored off site that I don't get to drive very often.
My E30 touring sat for 7 years...full tank of gas, stabil added before being stored. I always meant to get it out, but one summer turned into 2, then 3 then ....7 !!! Last summer I put in a fresh battery and it fired up first try. Being fuel injected certainly helped. I ran it enough to get it on my trailer and into the garage back home. I did drain all of the old fuel I could out of the tank and used a fuel additive mixed with new fuel for the next few tanks. No issues. I got rid of the old fuel by mixing it in my f150's 120 litre tank about 20 litres at a time. No issues there either.

My 240z has triple Weber carbs. They've been on the car for 20+ years. It always gets winter stored with stabil. Last summer I took apart the carbs for something to do. Clean as a whistle inside. Not a trace of varnish anywhere.

I leave my 930 parked for 6-12 months all too often and I haven't blown up the engine yet driving with the old fuel in it. It does have EFI though so no clogging up CIS parts.

You should still drive it off. Older gas can burn fine but leave deposits on the intake valves. Six months is when I feel compelled to burn it all out and start fresh.

We have a car in Florida that I affectionately call our 'POS' car, a 2002 Chevy Tracker. Basically the cheapest running reasonable car I could find locally on craigslist, it has survived living 100 yards from the ocean, and tropical storm Irma. For various reasons, it has sat unused for almost 2 years. Since we rarely drive it, and it had 1/4 tank, I'd say the gas was closer to 3 years old.

Today, filled pumped up the tires, put in a new battery, and it started right up.