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In the past I've kind of poo-pooed the "old gas" debate because gas sits in my mower and 38 all winter with no issues. That is until about a month ago. I've not driven the 38 nearly as much since getting the 53. Last winter's gas hasn't been renewed by new, fresh gas over the summer. I finally decided to get the 38 out of the garage a few weeks ago and all was good. I drove for an hour or so, still on last winter's gas, then put it away. About a week ago I decided to get it out again and was startled to have the starter drag so bad I thought the battery had died. It finally started and I discovered that the battery was good but stuck valve(s) were resisting the turning of the engine. CLATTER, CLATTER, CLATTER! What the heck??? It was running, barely, as I got out of the car to open the hood to see where the noise was coming from specifically. In the time it took to get my old, well fed body out of the car and get the hood open it started to quiet down and run more smoothly. It was at that time I decided it was sticking valves at fault and probably the old gas building up varnish on the stems that was causing it. I was fortunate enough that they didn't stick bad enough to bend pushrods (been there before). I siphoned out the remaining gas and disposed of it at the local hazardous disposal site. I poured in 5 gallons of fresh gas along with a can of Chemtool and started it back up (this was the next day). Sticking valve(s) again but not quite as bad. After about 30 seconds it smoothed out and ran well. I took it out for a drive to give the Chemtool solvent a chance to work and shut it off to sit over night. Next day no improvement. Two more cans of Chemtool, another 5 gallons of fresh gas from the station and a couple of hours of driving and I put it away again but with some trepidation. If it didn't improve I was going to have to pay someone to pull the head and clean the valve stems since I can no longer lift the head. I ventured out this afternoon and, with fingers crossed, fired it up with no sticking. YAY! Lesson learned, drive the darn thing!!! Gas CAN go bad after a few months, to the point of gumming up valves.

My Harley, my lawn mowers, pressure washer, concrete mixer, generator, and other occasional-use engines all get a regular dose of Sea Foam in the gasoline. It can't hurt, and I believe it helps the gas stay fresh.
Jerry

Can't argue that. I also put Sta-bil in the fresh gas.

If you guys remember, about 2 years ago I took 3 small jars and put gas in them. One was filled with gas that was about 4 months old, one with gas that was 2 months old and one with so-called fresh gas. I watched them all summer and little by little they all changed color. The oldest gas turned a deeper shade of yellowish orange, the middle gas did the same but not quite as deeply colored and the fresh gas by summer's end was about the color of apple juice. Then I poured out the oldest gas into the base of an upturned soda can and lit it. It burned extremely smoky, sooty and left a very sticky gummy residue. It also burned notably more slowly. Residue looked just like burned sugar or melted Saran Wrap. Same with all the others but the oldest was decidedly the worst. Why? Well, I discovered gas that had been sitting in my gas tank while I rebuilt an engine (took ~4 months) no longer was worth a flip. Below is an image. I'd be surprised if Sta-Bil or Sea Foam would help this but maybe. I think you have to use gas asap.

I stored a lawn tractor outside under a tarp, Sta-Bil in the tank with regular gas before shutting it off. FIVE years later I put a battery in it and started it up and it's still in use today. That's all I have to say about that.

Jon G, good research, I'm going to try and copy it so I can show the rest of my gearhead friends. Doc.

Can't believe it my medical background wife gave me the info on how to find out how much gas is in my tank. I took one of the laser temperature gizmo's that every restaurant, store,etc. that are floating around. I took it and focused it on the side of my gas tank. Where the temp dropped is the level of gas. Doc.

Can't believe it my medical background wife gave me the info on how to find out how much gas is in my tank. I took one of the laser temperature gizmo's that every restaurant, store,etc. that are floating around. I took it and focused it on the side of my gas tank. Where the temp dropped is the level of gas. Doc.

Thanks...use ethanol gas if you want to repeat what I did. I didn't stop studying this 2 years ago, by the way. I admit I'm a sucker for factual data and I admit I've always been curious. Actually I've read a decent bit about it since then. If you want more scientific data and research, I can give it or point you to studies that have been done. It all boils down to 2 words: phase separation. If you read only about that, you'll have a great understanding of why keeping ethanol fuel in a tank for longer than a month could be an unwise choice.

In a nutshell, what is needed to help solve the ethanol gas dilemma is to reduce phase separation...essentially more water must be held in suspension. Elimination of phase separation would be ideal, but from what I understand it would be chemically impossible. From every study I've read only 2 products have been proven to help do this (unfortunately Sta-Bil and Sea Foam flunked the tests and that is why I'm very lukewarm about using those at best). The only known way to help reduce phase separation is to add methyl or isopropyl alcohol in high purity doses and to use the gas asap. We know that 200 proof ethanol will help but this is not available as a fuel additive, and using it as a fuel additive would be cost prohibitive. The bottom line is alcohol is hygroscopic whereas gasoline (by contrast---because it does not bond hydrogen) is hydrophobic and that means alcohol absorbs water whereas gasoline will not absorb it. The whole idea behind the "gas life extending products" is that they will absorb water so that water can be passed through the engine without problems. In other words adding more alcohol will soak up water and hold it in suspension. But...there are limits. Once the amount of water in E10 gas exceeds .41%, that ethanol-rich water in excess of that small % is heavier than gasoline and it settles to the bottom of the gas tank. And then nothing good happens as it will never mix with anything. For a visual example, .41% of a 20 gallon gas tank equals 10.5 ounces or roughly 2/3 of a pint of water (2560 ounces x .0041 = 10.496). And as mentioned, that is the "safe" level. A greater percentage (which will indubitably happen given more storage time) means all the excess goes right to the bottom of the gas tank. Again, please study "phase separation."

Which 2 products were proven to reduce the phase separation and actually prolong gas storage life? HEET ISO Gas Drier and BG-Ethanol Fuel System Drier. But...and this is really important...the max % of water held in suspension using those 2 products was .43% and water started separating from gasoline again at .44%. A big victory? No. A very tiny success, actually. .41% v .43%. Baby steps.

Here are some other products which didn't work: STP, Valvoline, Rislene

Interesting Jon. Back in my Air Force days, we used to purge the water from the planes tanks. There were spring loaded access points under the wings. Supposed to catch in a jar but common practice was push with a screwdriver and let it squirt on the tarmac! Not very environmental, but then not much was then.

Dennis

If I'm reading that right, storing gas in air tight containers, filled to the top may allow longer storage since it's removing moisture laden air from the equation.

Tiny, I think that makes perfect sense. Now I will tell you this...I bought one of those new EPA mandated non-vented gas cans (they're all plastic) around 2018 and it is really interesting. Do you have one of those? In the summer it puffs up like a balloon (it will just about roll over sitting on the driveway) and in the winter it sucks in so much it nearly collapses. I'm not certain who thought that a vented gas container (a standard procedure for all of my lifetime) was so pitifully stupid it had to be abolished, but somebody did. And Bob's your uncle.

After I had a plastic gas can break and dump 4 gallons of gas on my feet I refuse to use a plastic gas can. I have two metal cans. Both have sealable vents.

It has been my experience that a fresh engine with new valves and guides will seize up in a short time sitting with old gas while a worn engine usually won't. I would guess there is an oil coating on a worn engines valve stems. A squeeze bottle of lacquer thinner with a "straw" nozzle will cut the varnish in the guides quicker than anything else I've found. Pulling the valve cover and dosing with thinner BEFORE cranking over can save headaches and dollars. After treating one can hear a snap when varnish dissolves, especially if the rockers are backed off.