What has happend to gas when it gets old and starts to affect engine performance?

What is actually happening to the gas? Can it be treated? And can you cause harm to your engine by running it with this type of gas? Lenny

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Gas is a mixture of all kinds of stuff. The light hydrocarbons evaporate. The medium hydrocarbons link up with one another and form varnish. Now that we have ethanol in gas instead of lead, much of the ethanol evaporates and what doesn't evaporate deliquesces and pulls water from the air.
So what you wind up is a uniform mixture of varnish, heavier hydrocarbons, and water.

Not really. You can dilute it way down with good gasoline and burn it a little bit at a time to get rid of it.
There are pretreatments that will prevent some of the breakdown if you have to store gasoline for a whole, but they aren't as effective as they were in the pre-ethanol days.

You bet. Varnish clogs up the fuel filter, it clogs up the injectors, water causes rust in the tank and in fuel lines which clogs up the filter and the injectors. The car winds up missing, running lean, you burn a valve trying to keep it running. --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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On Thursday, May 11, 2017 at 6:22:51 AM UTC+8, Scott Dorsey wrote:

I have run dual-fuel cars for many years. They start on gasoline, but soon switch to LPG. So little, that a tank of gasoline would last for years. However, stale fuel would stuff the fuel pump eventually. Did not find any other damage. I would have thought that evaporation of lighter fractions (pentane, hexane?) would affect cold starts, but that did not seem to occur.
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That's kind of cool actually! Maybe running on LPG cleans the injectors and lines out? How much of the fuel system is actually shared between both fuels? --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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On Friday, May 12, 2017 at 8:42:00 PM UTC+8, Scott Dorsey wrote:

I doubt any. Older systems just had a mixer next to the throttle. Since about 2005, sequential injected systems are needed to pass emission standards. So there are two sets of injectors. I doubt anybody made a flexfuel system for LPG, like with E85. The only liquid-injection systems I know of were dedicated LPG. But I imagine if you could force propane/butane though the fuel system it might work as a harmless cleaning solvent?
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Makes sense. Then all that I can think of is that the system was designed to deal with old gas since the manufacturers expected you to be driving like you do? --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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On Wednesday, May 10, 2017 at 4:05:15 PM UTC-4, snipped-for-privacy@gmail.com wrot e:

se harm to your engine by running it with this type of gas? Lenny
Thanks for the great explanation Scott. This vehicle had been sitting for t hree years with a full tank of gas in it. It started right up but runs like crap under load. When you mentioned addin g good gas to it and burning it off slowly did you mean just keep adding to it until you've done a complete transfusion to get rid of it or did you me an after you've pumped all this crap out of the tank? Lenny
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On Wednesday, May 10, 2017 at 6:59:17 PM UTC-5, snipped-for-privacy@gmail.com wrot e:
ote:

ause harm to your engine by running it with this type of gas? Lenny

three years with a full tank of gas in it.

ing good gas to it and burning it off slowly did you mean just keep adding to it until you've done a complete transfusion to get rid of it or did you mean after you've pumped all this crap out of the tank? Lenny
If it's been sitting for 3 years, take it to your mechanic and have him dra in the tank.
Andy
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Well, if you're lucky the only thing you've wrecked is the fuel filter. Dump the fuel, change the filter and see how it goes. Don't be surprised if the fuel pump fails in the next few thousand miles too, so have a spare.
It wouldn't hurt to pull the injectors and check the screen filters inside each one too. If you have one injector partly clogged, you wind up with one cylinder running leaner than the others which is a recipe for a burned valve.

I mean draining the tank, and once you have the thing running well and have run a few good tanks of gas through it, THEN burning small amounts of the bad gas. Take 20 gallons of good gas and one gallon of the bad gas.
If you dilute it down enough it won't be too horrible, and it saves you from having to pay a fortune in disposal fees to get rid of it. --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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In rec.autos.tech, on Wed, 10 May 2017 13:05:12 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

Dr. Solomon Petrol is known for his abiltiy to treat gasoline.
But it's a long, expensive process and the couch smells like gas afterwards.

I'm no pro, but I don't think so. Dr. Petrol says tha the gas needs self-actualization and that running the car with it helps in that.
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