What happens when good gas goes bad?

[PiratePast40]

There was just a tread here about using two year old gas. Water in the fuel and phase separation have been covered several times with the expected strong opinions both ways. I don't want to open up that issue but do want to ask about gas "going bad". What really happens? I hear about and have seen "varnish" in carbs but want to know what it really is and what is happening to the fuel. Not trying to start another oil, or additive type thread - just what happens, when, and how to tell when fuel has "gone bad".

 

[Frank Acampora]

Re: What happens when good gas goes bad?

Gasoline is a compound consisting of various short chain and long chain hydrocarbons from five carbon atoms up to hundreds. Less carbon atom compounds are more volatile and start easier while burning quicker. Many carbon atoms pack more energy per molecule. The specific mixture is set by the refinery.

It is not a really stable compound so with age the hydrocarbons tend to form other chemical compounds such as esters, alkyls, and ketones, and also polymerize into much longer and less volatile compounds. These compounds will still burn, but not like gasoline. This polymerization forms the "varnish" which tends to plate out on tank and carb surfaces. Very similar to fiberglass resin "setting-up" but much slower and less severe.

This is the simplest explanation so don't take it as the absolute. I figured you really just generally wanted to know what happens.

 

[BTMCB]

Re: What happens when good gas goes bad?

....others start leaving the room....

 

[RWilson2526]

Re: What happens when good gas goes bad?

Gasoline is a compound consisting of various short chain and long chain hydrocarbons from five carbon atoms up to hundreds. Less carbon atom compounds are more volatile and start easier while burning quicker. Many carbon atoms pack more energy per molecule. The specific mixture is set by the refinery.

It is not a really stable compound so with age the hydrocarbons tend to form other chemical compounds such as esters, alkyls, and ketones, and also polymerize into much longer and less volatile compounds. These compounds will still burn, but not like gasoline. This polymerization forms the "varnish" which tends to plate out on tank and carb surfaces. Very similar to fiberglass resin "setting-up" but much slower and less severe.

This is the simplest explanation so don't take it as the absolute. I figured you really just generally wanted to know what happens.

well it sure sounded damn good

 

[mphy98]

Re: What happens when good gas goes bad?

It has to go to rehab like jesse james and tiger!!!!!!!!!!

 

[PiratePast40]

Re: What happens when good gas goes bad?

It has to go to rehab like jesse james and tiger!!!!!!!!!!

I wasn't expecting that. Maybe something about tats, flashing gang signs, or pants on the ground! I really don't want to know too much more about gas and sex - just doesn't seem right to talk about it in the same conversation :redface:

 

[cr2k]

Re: What happens when good gas goes bad?

Short answer....It makes your engine run bad and harasses your carburetor.

 

[Silvertip]

Re: What happens when good gas goes bad?

Let's see. 1) starting issues, 2) idle issues, 3) loss of speed, 4) lean carburetion, 5) which leads to engine damage, 6) which leads to engine rebuild, 7) which leads to engine damage because 8) the original problem (lean carburetion) was not corrected during the rebuild. The long and short of the discussion is bad fuel can be prevented by using a fuel system treatment like Stabil or SeaFoam on a regular basis. Untreated fuel goes bad. Doesn't matter what chemical reaction occurs. It screws up carburetion.

 

[SeanMcl]

Re: What happens when good gas goes bad?

It also gets a sulfurous or rotten egg smell. And the taste of old gas is foul beyond belief, not that fresh gas tastes good or anything. Use a primer bulb to start a siphon, or prepare to abuse your gag reflex.