I have seen a case where really old gas glued all the rings in the ring grooves of the pistons with a heavy brown varnish, causing loss of compression and requiring motor rebuild. The cyl walls weren't damaged, but the rings got stuck in their most compressed state.

This particular car was typically run for several miles every year (start up, drive a mile every couple months), and I don't think the gas was changed for several years. I saw the pistons at a rebuilders shop, he told me the story about the car.
Doug

 

The referenced article is technically challenged, and I didn't see anything about a "shell engineer" and who is "Richard Newton" and what are his credentials?

Let's start with this quote:

"Gasoline is a highly refined substance with complex molecular bonds. Over time, these bonds break and the fuel reverts back to an earlier unusable state. As the molecular bonds break, the octane rating falls to the point where the gasoline is no longer able to produce the energy required for effective internal combustion."

What really happens is that over a long period of time - usually several years - the HC molecules slowly oxidize and eventually form gum and varnish, and this reaction rate increases exponentially with temperature, so the cooler the storage environment the better.

Also over time the lighter components, which are also the higher octane components can vaporize, which can lead to harder starting and loss of octane value, and this will occur more rapidly with vented fuel systems, and as with oxidation will progress more rapidly the hotter the surrounding temperature.

Back in the day water at the bottom of the fuel tank could freeze and leave the car stranded - happened to my SWC once circa 1965. There were various products on the market like "Heet", that were basically alcohol, which acts as a cosolvent that allows much more water to mix homogeneously with gasoline so it will be harmlessly consumed by the engine as the fuel is burned off. So, in a way ethanol is good because it takes a lot more absorbed water before the water/alcohol blend drops out, which will begin the corrosion process and often render the engine unstartable.

Oil company engineers that I have talked to have stated that the "shelf life" of gasoline is about one year, but the point was brought up: "What is shelf life". My definition is the amount of time before the gasoline significantly deteriorates is terms of octane or gum and varnish formation, and this is a function of the storage environment -sealed or vented container? Temperature? Humidity?

I think one year shelf life is conservative and may be absolute worse case conditions. As stated by many no problems have occurred with gasoline several years old, but as a precautionary measure I recommend consuming at least one full tank per year and keeping the car in as cool/low humidity environment as possible.

Duke

 

So, having both vented and non-vented gas caps, I should use the non-original, non-vented one for long term storage. That makes sense to me. But I have to remember to switch them before running the engine again or I'll experience stalling due to fuel starvation. That's happened before.

 

I had a hell of a time with my 67 327 .
I even wrapped the gas line with insulation .The gas would boil scared the heck outa me . It had a Holly Carb on it may have been the problem it was good after insulation.

 

I think '67s had pressure/vacuum relief caps with valves that released at about+/- 2 psi, but I might be wrong.

In any event, if you've had fuel starvation with a pressure/vacuum relief cap, use a vented cap during the driving season and install the pressure/vacuum relief cap during the storage season, which will slow the rate of evaporization.

Don't use a cap that is "non-vented", which means it lacks pressure or vacuum relief valves. That could cause the fuel tank to deform if the pressure or vacuum gets too high.

Duke

 

E10 has lower mid-range boiling points than typical straight gasoline, so vapor lock and percolation in the carb bowls can be a problem.

And because the fuel feed line to the pump passes very close to the exhaust manifold, fuel temperatures can exceed 150F before it even gets to the pump, especially in hot weather low speed traffic.

Insulating the fuel feel line to the pump in the engine compartment area can be very effective at mitigating vapor lock and percolation.

Duke

 

Thanks for posting Duke. That reference article is full of incorrect information.

 

I can see a run coming on non-vented gas caps starting any time now. I thought my original vented caps kept fuel just fine for a couple three years.

 

I've found an ethanol-free source not that far where I was buying my regular gas anyway - certainly can't hurt to try a few tankfuls. But I've NEVER had to resort to that in in 35 years of owning classic cars...

 

Bill

 

Running a 30-50% mix of 100LL and Sunoco 93 seems to keep things happy.

I drive my '66 a lot, so gas only lasts a week or two.

This winter the car sat for almost 3 weeks without being driven and it was sad. As soon as the roads were clear of salt and snow, out she goes!




Keep burning it, it's cheap!

 

I don't get it. What is this picture supposed to show?

 

For some of you youngsters, clipping clothes pins onto a car's fuel lines decades ago was a supposed cure for vapor lock.

Total myth of course.

 

Clothes pins on the fuel line was an old backyard way to help prevent vapor lock.

 

Generally followed by replacing the fuel pump.

Larry

 

It is, however, an incredibly attractive look

Steve

 

I use only ethanol free in the Corvettes.

I don't even use E10 in my lawn mower.

 

Easiest way to do that is get in and drive it as often as possible!

 

Ethanol=Net energy loser.

Carter

 

Hey, I wish I WAS a youngster!