We have all heard about unleaded fuel and its "shelf life". Does anybody know what happens in the fuel tank if you leave unleaded fuel for a long time. I have had a car which sits and I was starting occasionally and it ran and drove. On some occasions it seemed like it was out of fuel and I would top up the tank and it would start (sometimes very rough).This is an injected 5.7 GM motor so not easy for an old schooler to check carb, distributor, leads etc. Now the same thing is happening and I have added fuel again and still no start. Does the old fuel accumulate and maybe form a sludge in the tank. My gauge says it is nearly half full but I am wondering if I have a mass of something in the bottom of the tank and the fuel we add just sits on top and can't get through. When I do try to start the pumps run and I can smell fuel but no fire in the belly.
For decades I have parked the cars for the winter with a full tank of unlead with alcohol. They sit this way for 4 to 6 months. I start up and use the cars in the spring without problems. A full tank helps prevent condensation in the tank. I am on the side of alcohol additions to relieve us of imports and middle east wars but my cars do not care. The performance of the old fuel is possibly lower than fresh but I do not care if they start and run the tank down to refill level. I have not had problems with fuel pumps, carburators or filters from this practice.
Seafoam or sta-bil marine grade & marvel mystery oil added to the fuel before you store the car & be sure to run a lot through the engine before you shut it down. I have been doing this to my fleet for years & never a problem & they fire right off. A qt in the engine oil(do not overfill) won't hurt either.
I park my 36 in November and start it periodically, then in march, she gets flashed up on the same gas and driven till its empty. Doesn't worry me.
Gas is funny, you never know how well it is going to store. Some of it goes bad quickly and some stays ok for longer periods. I just bought a car that had been sitting for 4 years with 9 gallons of fuel in the tank that had not been stabilized. I put a battery in the car and a quick squirt of starting fluid in the injectors, and it fired up and ran like the day it was parked. I expected pinging and poor running, but I got none of that. But generally, if gas is over 6 months to a year old it starts getting bad. Products like Startron and Marine Formula Stabil seem to help, but I have had techs tell me even those cause their own problems because they gel in hot climates. So who knows. Don
Having spent 5 years in the fuel industry and running my own tests I did find that Exxon/Mobile fuels worked better and gave better scanner readouts, o2 etc. They are pretty adamant about their additives and getting their product into their tanks. So much that a store could lose their franchise if there was a mix with the wrong gas. We are talking 250k-a million or more loss. I trust their fuels. But, I was an insider for many years as I said.
I fill my tank in October,prop the hood up some so no moisture gathers and make it a point to start it every month and bring it up to running temp.,put it in gear come against the converter in drive and reverse and in 15 years haven't had any issues yet
Gasoline is less stable in direct sunlight or warmer climate. I had a motorcycle that was black. It sat outside one winter exposed to sunlight. I couldn't even light the gas with a match in the spring. The bike would not start either. Gasoline in shaded cold winter storage has not suffered as severe degradation. I put gasoline in a open glass jar in direct sunlight on a hot sunny day. Weird thing started to happen in the gas. It stratified into several different layers, formed precipitates in some layers while others remained clear. The precipitates moved around in the layers from heat convection. I think it was drained out of an old tank so the gas was old to start with. Old gas bad.
That is called "Phase separation" and is one of the problems ethanol gas has. Stabilizers are supposed to keep it from separating out like that. http://www.wellworthproducts.com/articles/phaseseparation.asp Don
THIS...^^^...Gradual changes in temp have little effect. Cars stored in garages and cans inside. Even if the the temp goes to 0 in the winter and 100 in the summer, the gradual changes help prevent the separation and gassing off of the volitales. Outside storage is bad as is sun shine on the containers or tanks. And remember when we added dry gas to absorb moisture? All that was was alcohol. We already have enough alcohol in the gas to absorb water in large quanities. Don't add any more!!
There are small very fine mesh screens on the fuel injectors.They are probably plugged up with gummy/varnish substance from old gas. I speak from experianc as I had a 350 TBI motor in a donor vehicle for about 10 yrs that I would start and run twice a year. the last time I tried to start it. It acted the same way I was trying to move it to the shop to pull the motor. So pulled the injectors apart and found the screens clogged up. You should hear the electric fuel pump in the tank run when you first turn the ignition on. If you do not then the fuel pump could be rusted/ seized. Trying rapping on the bottom of the fuel tank with a rubbber mallet. This may jar the fuel pump enough to run also.
i had same problem. go 100 gals of free 2 year old gas. tried mixing it 50/50 with new gas and it worked but it was also added to my oil level in the pan.i guess there was a part of the old gas which would not burn and was washed by the pistons and into the pan.same thing when you poured some of this old gas on the ground and threw a match ;it would hardly burn?the vehicle was a tbi 99 chev 1/2 ton.maybe it would work in a carb fed engine?Might be able to add a little to my furnace oil?
the larger the amount stored the longer it lasts, 20 gallons will last for months but half a cup will only last a few weeks.
It also matters what kind of tank you are storing it in plastic cans and plastic tanks allow the gas to go bad faster if you have a metal can or a metal tank your fuel will last longer. I don't have any numbers but from experience this is what i have noticed.
I always store my Acadian from about November till March. I start it about 4 times between that time and have never had a problem.
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