When is "old gas" too old to use?
 

An article on Autospeed got me wondering about this.

I was surprised to read the experts giving answers that were much shorter than I would have expected.

Depending on whom you ask, gasoline is good for ...

• 6 months - in a sealed container, after which it starts to degrade
• up to 12 months in a sealed container
• "several months" old fuel in your tank risks fuel system problems
• "several weeks" is enough to detect octane degradation, based on dyno testing

Read more from: The Life of Fuel - How long does fuel last in your car's tank?

When I got the Firefly, it had been sitting, the tank nearly full, for seven years. The engine started normally on the old gasoline, and it ran apparently fine when I test-drove it around the block.

http://metrompg.com/posts/photos/ACFC07C.jpg
7 year old gas

7 years seemed pretty extreme, though, and I was warned that old gas could gum up the intake valves and make them stick. So I drained the fuel tank to nearly empty, drove straight to a gas station and filled up with fresh gas before driving it home.

OK, so if 7 years is too much, how about four years? That's how old the gas is in this 1990 Swift GTi:

http://ecomodder.com/forum/attachmen...1&d=1315783546
4 year old gas

... and with a boost, it started right up after sitting in a field for that long.

On the other hand, I have had trouble running a 2-stroke boat motor with fuel that was 2 years old. Maybe it depends on the engine, or the oil mix causes things to go wonky sooner.

Autospeed: The Life of Fuel - How long does fuel last in your car's tank?

I have a 1993 Toyota Tercel sitting in the driveway. I know the gas is at least 4 years old. I fire it up a few times a year to keep things oiled. Never has any issues...

...my lawn-mower sits all winter, and seems to start OK each spring.

Most modern cars have sealed gas tanks so very little fuel vapor leaks out, they also have fuel injection so there is little to no air in the rest of the fuel system.
Motorcycles that have gasoline that is 9 months old or more tend to have issues because there are so many vents in the carburetors and the gas cap is more or less an open vent, because of this the volatile part of the gasoline evaporates and escapes leaving behind varnish, this is often made worse with ethanol in the gasoline because the alcohol sucks up water out of the air the ethanol then easily evaporates leading to water in the gas.

So I figure if gasoline is in a can or tank that is vented it has a shelf life of 6 months before issues start to show up, if it's sealed in a safety can, or the gas tank of a vehicle with fuel injection it's good for a year or more.

The motorcycle shop that I used to work part time at has a lot of motorcycles come in every spring with bad gasoline and I still get calls from friends who have lawn mowers that have year old gas from a gas can put in them and don't want to run, change the gas and they run, put that old gas in a fuel injected car and it will run as well.

I store quite a bit of gasoline in proper 5 gallon storage containers. I've had some of it for up to 2-3 years, still usable, with no bad effects. The worst part is that some of the volume will be lost to evaporation, no matter how you store it.

Gasoline contains additives. If you are going to leave gas in a snow blower or lawnmower, either drain the tank completely (preferably) or keep it entirely full. Gasoline contains additives. If you've ever had to rebuild a lawnmower carb you might find it full of goo from someone who left it sitting for several years with gas still in it. The gas evaporates and leaves a lot of residue that clogs the carb.

That must be why several old-timers that I know with outboard boat motors will disconnect or shut off the fuel line to the engine -- while it is running -- several minutes before they plan to stop it. Then let it run out and stall when they've docked, with the carb dry. They do this if it's going to be sitting even for a week or more.

My 1968 Chevy pickup had gas in it that was about four years old. It ran just fine, but the filter clogged pretty quickly. No sealed tank here.

I've since drained the rest of the gas out until I can more regularly drive it.

I've known of several cars that ran fine with 4+ year old gas in the tank. On the other hand, we run our outboards dry as well. (It's amazing how long a Honda 5 hp 4-stroke will run after you disconnect the fuel line.)

The issues with old gas include varnish and varnish flakes that clog up jets in smaller engine carburetors, so a 1.5L carburetor is going to clog up more easily then a 6 litter engine on a truck would, so a string trimmer is going to be fussy while a tractor might not be, and on something like a 2 stroke out board engine that is sensitive and will burn a piston if you run it lean it's best not to risk a partial clogged carburetor, where an old single cylinder John Deere tractor doesn't even care if there is water in the gasoline.

Exactly. I'm "on the wrong side of fifty" and I always do this with my snowblowers. They are 50 and 40 years old, respectively. (I bought both of them used and have had each of them for "only" about 25 years.) One had a gas tank that was full of rust and crud when I got it, and I had to put a replacement tank on it.

Some winters are mild and you might only need to use the blower a few times. No matter. I installed a shut off valve in the fuel line and let it run until stalling out whenever I use it. Then I empty the gas tank fully at the end of the season. With the lawnmower I only empty the tank out when putting it away for the winter. You'll never go wrong in doing that.

Back during the first oil embargo, I was working on a ranch with a fairly large "junkyard". Whenever the owner bought a new something, he'd just drive or haul the old one out to the field back of the barn & park it. (Scored a repairable Sunbeam Alpine and one of the first Toyota pickups in this country from there :-)) So when the local station was out of gas, we'd go out with buckets and drain the tanks of the old cars & trucks. Seemed to run fine.

I think the issue with small engines & such is not really the gas itself, but the varnish & crud that builds up in the system from the gas just sitting there. But if you put that same gas in a different engine, it does ok.

I stored a Honda Insight for 2 1/2 years, with Sta Bil in the tank. I had the engine run about 9 times in that period.

No problems on startup.

I've had gas that was just over a year old sitting in a gas can not work in a lawn mower so my family has taken to tagging and dating gas cans when they get filled so we don't end up with gas that is years old.

Yet another reason I'm glad I bought an electric mower :-)

It's not the gas. As I mentioned, I have some stored gas that is older than that, and it works fine.

What probably occurred is that you left enough gas in the tank and/or the carb (over winter) for it to create residue and clog the carb. Also, if the machine is getting older, it might have been due for a carb clean out anyway, and it was coincidence that the carb happened to poop out when you put gas in it.

I tend to either run my snow blower and motorcycle out of gas before storage or drain it out the drain plug in the bottom of the carb, I've also put old gas in a small engine that had been running up to that point and had it smoke and stall and found the fix to be as easy as fresh gas, I've had that happen enough times that asking how old the gas in the tank is, tends to be one of my first questions when fixing a small engine.

I always add Stabil to every can when getting gas for my small engines, as I don't go through it that fast. Always make sure the can is tightly closed as well.

I've recently found Regular gas without Ethanol that I use in the cycle and small engines.

I also drain the gas from the small engines, run them dry, and change oil before storing every year. They always fire up immediately when needed.

As it gets colder I make sure to use up all of the summer gas that I have sitting around. If you happen to have a small generator, be sure to swap the gas regularly from summer to winter (and back) every year and run it - before you need it

Simple stuff that saves problems and headaches later.

So, it sounds like small, carbureted motors generally tend to not do as well as larger FI motors on old gas.

How old is too old? It depends. If it runs bad it's too old.

My experience is that winter fuel goes bad faster than summer fuel. E10 goes bad faster than straight gas. Mixing some new fuel with old/bad fuel can get the batch to a useable state, better to use old fuel than use it as a grease solvent, weed killer or fire starter.

If it is unsealed, then eventually you will get a gummy/shellac-like crust that has to be scraped out. I bought a 1976 Yamaha XS-650 back in ~1983 and the float valves were stuck and wouldn't let any gas into the carbs. I had to manually scrape out the gunk that was left inside.

If what I've heard is true, the new gas is even worse.

I saw a new (at the time) Honda Valkyrie 6 cyl with 200 mi on it in the service dept at the dealer with the carbs pulled. Turns out they prepped it and then stored it in the warehouse for a couple of months. In that time the carbs were gummed-up enough that they had to be removed and cleaned.

I regularly use Stabil in my gas, but Seafoam also claims to be a stabilizer. I've used Seafoam as a fuel system cleaner, but not as a stabilizer. As a rule, after running my "storage gas" through the cycle I will use a fuel system cleaner on the next tank. I like Techron Concentrate or Seafoam (1 oz per gal), and not the cheap-o "fuel injector cleaners".