How fast does gas go bad these days?

[Utah Blaine]

Could six month old gas cause the engine to miss, knock and blow smoke?

 

[ek02]

Six month old gas can cause problems. I was not able to use my boat for 6 months after Hurricane Wilma due to work and the closure of the area I fish. The carb floats stuck in the up position and it would not take off when I went to use it. I use Stabil at all times now in my boats and my generator gas that I store during hurricane season. It lasts for a year with no problems. I also use it in race gas and it remains good even after a year.

 

[b4black]

If sealed, gasoline will last a long time. Our systems are not completely sealed. Two things can happen. It can absorb water and the ethanol will 'phase separate out'. This didn't happen to my car that was unused for about three years. If it does happen, it should be pretty obvious. Disconnect the fuel line from the pump and drain some gas out. If you see two layers or water drops, it's wet.

It can also go 'flat', loosing it's light ends. In that case, my car would bog on acceleration, but otherwise ran ok (no misfires). Topping off with fresh gas should fix this.

If you let gasoline evaporate out of a carburetor, it could leave behind some scammer material which will plug things up. The more additive in the fuel, the worse this can be.

 

[Utah Blaine]

I let the car sit for six months while I fixed a oil leak. It ran pretty good except for a slight miss. When I started it back up it blows smoke, runs rougher than a cob and sounds terrible. It sounds like the pistons rattle and all manner of stuff going on.

Maybe some octane booster and Stabil will help. If not, off comes the gas tank again.

I have a couple of q-jet book coming (thanks Rich). Maybe adjusting the carb will help. The rattle or knocking bothers me though. Can't figure out what that might be.

 

[Nick Micale]

According to the "experts", they state that pump gas octane will start to deteriorate in 3 weeks, and at 6 months it will be down many points. This is applicable to gas in a vehicle, not stored in an air-tight container in a cool place.

Leaded gas does not have this quick deterioration, especially the higher octane race gas which I have tested after 2 years is still good if stored properly.

I use a gasoline stabilizer like Driven or Stabil in all my vehicles including the e-85 ones, except for the 2 daily drivers!

There is one exception, my 1987 9000 mi. original T always had 110 octane since new, still starts, runs and drives like.

 

[Utah Blaine]

Thanks, low octane must be the knock or clatter I hear. It only happens when I rev it up and let off or when the idle sounds like the engine is about to die. It just doesn't want to run. Funny, it starts right up.
I'll see what I can figure out next week.
Thanks everyone!

 

[Utah Blaine]

It was the gas, no doubt. Added some octane booster to the tank and it didn't do a thing. Pumped the tank empty and put fresh 92 and some gas stabilizer in and it ran good again. Had to let the engine run for a while until the stuff I put on all the bolts around the down pipe to burn off. The stuff must have soaked in around the donut like gasket. Sprayed it on all the bolts around the turbo and carb so I could take them off. It wasn't just smokin' out the tail pipe but off the up and down pipes and everything that caught a drop of that stuff. All burned off, new gas and no more ruff running engine!

 

[Farmer]

Can I put one gallon of e85 and four gallons of 92 octane in a five gallon container and use it in mine next time I need gas? Will it hurt the carb or anything? I don't hot rod the car any, just don't drive it much and I know the octane does a vanishing act in the tank.

 

[b4black]

The octane will only disappear if you let the light, volatile parts evaporate off. Keep the 92 sealed up in the five gallon container and it will be fine. If you add e85, it will mess with the air/fuel ratio and the engine will run lean.