What can I add to old gasoline to make it run?

I've some old gas in one of my cars that I don't drive. I start it and let it run occassionally, but the gas has gotten old enough that it will not idle at all. I have to continuously feather the throttle. What can I add to it to make it run enough that I can burn the old gas out of it? Isopropyl alcohal? Octane booster? Something else? I could probably add just add several gallongs of premium gas to it but I don't want to add more gas to it, just to have it go bad again in the future.

 

Drain as much as possible out of the tank, add premium to the remainder. Don't use it, it will screw up your carb/injectors.

 

race gas....the higher octane will mix with the old gas and make it all work...

 

Once you've cleaned it and added good gas, you'll need to add a fuel stabilizer to preserve it for the future. Also, be careful working around the bad/sour gas cuz it will make you sick and nauseated with a headache.

 

I put Stay-bil in the gas when its going to sit a while. Its a fuel stabalizer and its supposed to keep the gas from breaking down over time. My suggestion in your case is to drain the gas out and put a couple of gallons of fresh gas in and maybe some berrymans B-12 to clean out the fuel lines and carb. Let it run a while then put some more gas in it with some Stay-bil to keep it fresh. If you still have an idle problem then its time for a carb rebuild.

 

Drain out that gas before you ruin the engine...
I had to R&R a head on a 235 Chevy once where the guy did the same thing you're doing, running on bad gas.
Bent all the push rods, and we had to air chisel the valves out of the head
Drain the gas, then use Berryman's B12 or Lacquer Thinner to flush tank, carb, & lines, then add fresh gas.
Note: Sta-Bil is good, or use Aviation Fuel. It won't go stale for years...

 

Thanks for the suggestions. I know that draining the old gas is the "right" answer, but I'm trying to avoid that for a number of reasons...a big one being the disposal problem.

I've never had to use Stabil in it before, because up until the last time I added gas, I had used premium. It takes longer to lose its octane...maybe because of better additives...maybe because it has more octane to lose and takes more time. I made the mistake of putting in regular grade last time and it lost its "oomph" before I thought it would.

The gas is just slightly old, so I don't think it is gummy yet. I *think* that it has just lost its octane rating.

I actually had this problem on two cars. On the other one, I didn't mind adding more gas. I just added premium (making about a 2:1 mix) and it fixed the problem. I didn't want to add more gas to this one, but it may be the only answer short of draining the tank.

 

There's no way I would use that shit- so not worth it.

 

I'll second the recommendation to get rid of the old gas because of head problems, it sure can make the valves stick and cause mayhem.

 

Yikes! Had he tried anything else as an additive, or did he just run the bad gas?

 

Add some fresh gas and if you're just idling the car and not driving it, crank up the idle speed until it runs steady.
It won't hurt anything for the engine to run at 700-800 rpm once oil pressure is up.

Once the engine is warm, you can lower the idle rpm until the run period is complete.

I don't understand why premium would help unless the engine requires premium in the first place.

I do understand that the lower octane stuff (87) starts easier than the higher octane fuel all things considered.

 

I *think* that when today's gasoline gets old (about 6 months and sometimes less), it loses octane rating. And I think that adding premium brings the octane up to an acceptable level. But, I'm not sure about that. I do know from experience, though, that adding new premium to old gas will, at least sometimes, make the old gas run. I did this with the second car over the weekend. It would not run on the old gas. It would hit and run for about 10 seconds. I added the premium and it would start, run, rev, and idle properly. That engine is a high compression engine (11.25:1). The one I'm working with now is a low compression engine with a supercharger. At idle and low rpms there is no boost, so I don't think that's a factor.

 

Premium, my ass.

"Premium" is not any different than regular, except for octane.
Each refiners different fuel grade has the same additive content with the exception of octane. They all have the same BTU content.

The marketing department calls it "Premium" or "Super" so uninformed people equate it with "better" and will pay for something they most often don't need.

Octane makes fuel LESS volatile not more. That's why it is necesary in high compression or hot running engines- it's LESS likely to detonate/preignite and cause pinging.

If you want "hot fuel" that ignites easily, use a low octane, not high.

 

Used 6 month old gas in my lawn mower and clogged up the carb. which resulted in a huge loss of power. Fortunately a spray can of carb cleaner fixed the problem.

 

If it won't idle, varnish may have already clogged your idle circut in the carb. I would remove the carb and clean it. Sometimes, I have had success by pulling the idle needles, squirting some carb cleaner in the passages and the air vent ( to fill up the float boww, waiting a day, and blowing the passageways with compressed air. I am not proud of it, but it has worked. This is one time I would be grateful to have a Holley, they are so easy to pull apart for this kind of repair.
Bob