Fuel Expiration Date...?

ranger29sailor · Nov 23, 2009

You can always tell when your gas goes bad, because it stinks! It'll smell like turpentine or something, but not gas. I was a mechanic back in the day and people would bring in generators or other small gas engines that wouldn't start to the shop. Once I took a whiff of the gas, I could tell right away. You will too. Once you smell it, you'll never forget it. If it goes bad, just drain the tank and refuel with fresh gas. You might need to use some starting fluid to get it cranked up, but it should burn off the old gas quickly and you'll be on your way.

jimford2158 · Nov 23, 2009

The safest thing is to pour the old stuff into your car and buy some fresh fuel.

I agree with stan, even with oil added in, it won't hurt your car. For 25-30 bucks worth of gas, would you want to be left stranded. also, the oil will settle out of the gas, you will know this by how much it smokes, and then the engine will be running with too little oil. fresh gas will have fresh additives to clean the fuel system, if you use a name brand gas.

Bruce Roberts · Nov 24, 2009

My experience with the gas,have run a marina store for 3 1/2 with 285 boats and 5 years with W/M,I have found that
the ethanol was eroding the old hoses and gaskets on motors with carburators as well
as lawn mowers etc. Several products have worked well MDR#574 E-ZORB, water remover,MDR #551 STOR-N-START gas stabilizer, Startron # 93016 Enzyme fuel treatment, also have a number of great diesel products as well, Howes, MDR, Startron to name several

HukilauMike · Nov 24, 2009

I put sta-bil in my gas tank along with the two stroke oil every time I mix up a new batch. I use less than 9 gallons a season, and I keep the leftovers in my garage over the winter. Before using the leftovers the next season, I will sometimes add fresh gas/oil/sta-bil to the mix, and I've never had a problem. Btw, buy the Sta-bil at Walmart, an auto parts or hardware store. It's about half the cost there than at West Marine or a chandlery.

divinebovine · Nov 24, 2009

I work for a little airline in Vancouver, BC and we cycle the gas in our spare tanks every 6-9 months... I've been told that gas more than a year old shouldn't be used... that may just be in aircraft, but I like this 12 month rule.

RichH · Nov 25, 2009

Carburetors (with floats that control the static height of the fuel over the main jet, etc.) are VENTED to the atmosphere. The cause of the formation of gums and 'varnish' in the carburetors is the off gassing of and separation of the various 'fractions' that compose 'gasoline' .... out of the vent and progressively and additively leaving the heavier fraction in the bowl. The smaller the carburetor the greater the 'propensity' of the gums and varnishes to occlude or change the functional geometry of the 'teeeeeny' orfices and air bleeds in the carburetor.
Most 'fuel stabilizers' are similar to or ARE polysorbate-80 a compound that also is used stabilizes foodstuffs containing 'edible oils, etc. .... cooking oils, mayonnaise, salad dressings, etc.

Shelf life of gasoline is about 1-3 months depending on the ambient temperature.
This has NOTHING to do with water, 'condensation', etc. but rather an 'organic chemistry decomposition' process that is enhanced by the contact with oxygen in the air.
Without adding stabilizers the only way to retard such decomposition/volatization is to 'blanket' the fuel with an inert (nitrogen) gas, etc. .... remembering that fuel tanks also have atmospheric 'vents'.

Sooooo, the BEST to protect against gums and varnishes is to 1. add a stbilizer; 2. shut down the fuel supply and run small engines 'dry'.

3. for long term storage, after 1&2 above, remove the idle and main jet needle valves and 'squirt in' some isopropyl alcohol (and drain) to remove any small deposits that have formed.

Fairwind · Nov 25, 2009

Unstabilized gasoline is good for 6 or 8 months, no problem. With Stabil added, it's good for over a year in a full semi-sealed container. Good advise about running carburetors dry or draining them. Cold prolongs the life of almost anything, including gasoline. In high temperatures, it will degrade much faster..Two years is the practicle shelf-life when properly stored and stabilized. "Condensation" is an urban legand. Gasoline has a property called "vapor pressure" which prevents moist air from entering gasoline tanks. They are constantly out-gassing..Diesel is more stabil and has a longer shelf-life.

Truly degraded gasoline that smells like old paint and looks dark orange in color should not be burned in ANY engine. Unwanted but not degraded outboard mix can be burned in your car in modest quantities. (3 gallons per tankfull)..

catsailor · Nov 25, 2009

Wow. So much mis-information in one thread...

My apologies to those who got their facts straight.

1. Gasoline will not separate from oil. Ever. If it did, there gasoline would have floated out of the crude oil during the last 100 million years... but it did not. Niether does alcohol float out of beer.

2. The antioxidant in Sta-bil, Techron, and some other leading stabilizers are phenylene diamine derivatives. You can often detect the tell tale faint amine smell. The naptha is simply a solvent, though it has some cleaning function.

3. Condensation is not a significant issue in tanks, but absorption of water from the atmosphere is. E-10 will pull water from the air, much as calcium chloride pulls water from the air. I have been able to recreate this effect in the lab, under real-world conditions, in just a few weeks. So keep your tank full; refill upon returning to the dock or trailer, not when you head out.

4. Cold is not "bad" for gas, but it can trigger phase separation. Please read the following EPA memo on the subject. http://www.epa.gov/oms/regs/fuels/rfg/waterphs.pdf

5. The only additive tested to prevent phase separation is MDR-esorb... but it can also dissolve saltwater in your gas, so be careful. I tested all of those mentioned in the lab, but I could have missed one.

6. The big separation risk factors are: tiny water leaks - each ml will take 9ml of ethanol with it; tanks that are exposed to the sun, including integral tanks, because they temperature cycle more; cold weather, because it lowers water solubility. Thus, some boaters will have no trouble and credit an additive. Others will have trouble in spite of an additive. Antidotale information from other boaters is not helpful unless carefully examined.

Disclosure: I have 25 years in the refining industry. I am not connected to any additive manufacturer. I really wanted one of them to work, for my boat. Only a full tank works, by limiting breathing.

So keep your tanks full and happy Thanksgiving!

BobM · Nov 25, 2009

Well for aircraft...

divinebovine said:
I work for a little airline in Vancouver, BC and we cycle the gas in our spare tanks every 6-9 months... I've been told that gas more than a year old shouldn't be used... that may just be in aircraft, but I like this 12 month rule.

...bad fuel means a gravity check. A sailboat is just going to float!

BobM · Nov 25, 2009

Glad to hear it.

catsailor said:
Only a full tank works, by limiting breathing.

So keep your tanks full and happy Thanksgiving!

The full / empty tank thing has been discussed many times. I always leave mine full, because (a) it is easier than leaving it empty (b) although I knew the condensate issue to be bogus, I figured that water absorption would be a function of the headspace in the tank.

bffatcat · Nov 26, 2009

outboard fuel

On my old 2 cycle merc I had no gas problems

I bought a new 4 cycle 8 hp Tohatsu in 08 Its very stingy on gas and runs very lean. The dealer told me 1 month on the gas and put a capful of startron in a 3 gal tank I think that stuff is cleaning fluid. He said dont do it and your gonna wind up paying me $100 or so to clean out your carb. If there is anything left in the 3 gal tank I dump it in my gas tank no trouble yet

KJH · Nov 27, 2009

This has been a fascinating exchange of ideas and opinions! In a related matter, to add to the mix, so to speak, has anyone had any experience with a synthetic 2 cycle engine lubricant(oil) called OPTI-2? It's put out by a company called Interlube International of Blaine, WA? Supposedly 1.8 oz of this synthetic oil mixed with one gallon of unleaded gasoline is compatible with any 2 cycle engine regardless of fuel/oil ratio!! It even contains fuel stabilizer and keeps fuel good for a year.
I bought some for my snow thrower and the salesman assured me that it would work "great" on a marine outboard engine. I would be interested if any sailor(s) has tried this product in a marine outboard engine I would appreciate your feedback.

kerry sailor · Dec 2, 2009

The link below is good info on subject. Smell it you can tell right away if it is starting to go bad. My experience if gas is getting unuseable it changes smell and should be trashed.

http://www.straightdope.com/columns/read/2668/why-does-gasoline-go-stale-so-quickly

LordNelson · Dec 2, 2009

don't put an 40:1 oil/gas mix in your car as suggested or you could end up with worse problems.

i had trouble with low rpm idle on a 4 stroke 5hp honda this summer. i tried adding gumout to the fuel, which already had stabilizer in it. i ran the motor hard for an hour and it cleared it out. it ran better on idle, although maybe not perfect. it got me through the season anyway.

i use the left over fuel in my snow blower and lawn mower to get rid of it.

catsailor · Dec 2, 2009

Not a viable source of information, I think:

kerry sailor said:
The link below is good info on subject. Smell it you can tell right away if it is starting to go bad. My experience if gas is getting unuseable it changes smell and should be trashed.

http://www.straightdope.com/columns/read/2668/why-does-gasoline-go-stale-so-quickly

A few of his errors:

* E-10 does not suffer from condensation. Impossible with this chemistry. Phase separation, yes.

* Bacteria. Never. Diesel, yes, gasoline, never. Far too toxic, but Google it and check.

* Fuel drier won't help with e-10. It already contains too much alcohol.

* E-10 "might" be contaminated more easily? He has not done even basic homework in this area. EPA published data re the problem.

So, he's just another guy. Not the straight scoop, I am afraid.

The real answer, I'm afraid, is to sail more often!