how old can fuel be in the fuel tank before it goes bad.

jk911 · 11-03-2002, 01:31 PM

My car has been sitting for a month and the fuel has been venting lightly through the ventilation port on the top of the tank. Is the fuel still O.K . if not what should I do ?

Wayne 962 · Wayne 962's Garage

I give fuel a shelf life of about six months okay, and one year max. (empty tank after that point).

-Wayne

Bill Verburg · Bill Verburg's Garage

It's highly dependant on volume, my lawnmower gas will be bad after 6 mo. as will the snowblower. The car has always been fine for at least 6 mo probably up to Waynes # 12mo A fulltank will have fewer potential issues than a partially full one, w/ increasing potential for trouble as the gas level goes down.

jk911 · 11-03-2002, 02:28 PM

Thanks guy's

Is there an additive I can add to help the situation ie octane booster etc.

It has Lead replacement fuel .

maxnine11 · maxnine11's Garage

i had a corvette that had the same fuel in it for seven years. Parked it with a full tank with fuel stabilizer. Started it once or twice a year. Each time taking a small jerry can of fuel and more stabilizer to top it up. Believe it or not (I barely could), it would fire right up every visit. ( I did arrive with a freshly charged battery each time).....so, fuel stabilizer does work. .....Max

TimT · 11-03-2002, 03:56 PM

Use a product called Sta-Bil. its available many places

pwd72s · 11-03-2002, 04:36 PM

Sta-bil for me too. A full tank gas with it goes in my car every October. I run the car every few weeks through the winter long enough to get the oil up to temp. When the tank gets to 2/3 or so, I top it up with a mix of fresh gas & sta-bil from cans. Seems to work fine.

Bobboloo · Bobboloo's Garage

I once had a car that had sat for a year because of smog problems(computer).
Well I decided to drive it to the junkyard to get rid of it.
It was real low on year old gas so I added a gallon of some gas I had in a can in the garage. Then I remembered (unfortunately after I poured it in) that that gas was over ten years old that I had emptied out of the tank of my project car when I got it. Oops. So I added a can of stabilizer and drove it to the junkyard. No problem. It didn't even sputter or cough.

Bobby

diverdan · diverdan's Garage

I was gone for two years. 2 928s in the garage fired right up. I always make sure the tank is topped up before I store the machines. Good grief, I forgot about one of the 911s. It wil be 3 years before I get back to it .

Diverdan

speeder · speeder's Garage

I just started my BMW that had sat for at least a year w/ 1/4 tank of gas in it, (car was in pieces), no problemo. Ran like an open sore.

sammyg2 · 11-05-2002, 06:52 AM

Two things happen to gasoline over time.
1st) the octane drops about 1 point per month for the first few months and then eventually stabilizes.
2nd) the molecules of "reformed" or "cracked" gasoline are a little less stable than straight run gasoline so they can break down leaving wax, varnish, and free carbon molecules.

Sta-bil is a very good product and I use it in my personal watercraft every winter, but it can only do so much.
Old gasoline will burn and make a car go, but I would be nervous using it in a high performance engine that was pushed hard.

It also depends on the geographic region. Temperature plays a part, the hotter it is in a area the higher the tendency for evaporation, although warmer climates usually require fuels with a lower vapor pressure. The lower the VP rating the less the fuel will evaporate. Smog laws usually dictate that.
In So. California we used to have a higher VP rating during the winter months and a lower rating during the summer, but CARB phase 1 &2 basically changed all that.