?isopropyl alcohol

I am a firm believer in the use of isoprpyl alcohol in fuel systems to prevent winter driving issues.Recently I’ve heard that with todays blend of ethanol gasoline that this is no longer recommended/or may be harmful. What is your thought?

I’ve been driving since the mid '80s (admittedly not real long), and I’ve never had winter fuel system problems, even in 0 F weather with a carbureted car. These days, I think they’ve got all the fuel additives right at the pump, and modern fuel injected cars are much less of a hassle in the winter.

Some types of alcohol (particularly methanol) are very corrosive. I wouldn’t put isopropyl alcohol in my fuel and risk harm trying to fix a nonexistent problem.

I think this is another case of trying to deal with a problem in 2010 that hasn’t existed since the 1960s.

We don’t have ethanol blend gas but today’s gasolines have many additives and a smalll amount of moisture is of no concern.

However, in very cold weather ( subzero), and when I have to park in an underground heated garage, I still put in a small bottle of “gasline antifreeze” per full tank.

You are probably referring to back in the days when carbs ruled the earth, and cars experienced carb icing under cold conditions, along with high humidity conditions. Typically, most heat riser systems on carbs either were disconnected, or didn’t work very well. Alcohol was added to help prevent some of the carb icing, but never resolved the issue entirely.

If you have a car with a fuel injection system, this isn’t an issue anymore.

This still occurs with some motorcycles that are ridden in cold, humid conditions, that have carbs. Some bikes allow you to retrofit a carb heater kit to try to help with the issue. Those don’t always work either, however.


If you buy gas with 10% ethanol, you don’t need the isopropyl alcohol. Google “Dry Gas Wiki” for more on this for a view subject to scrutiny.

Before 10% ethanol gas arrived I never used isopropyl alcohol anyhow and never had a problem with a frozen fuel line. I have lived in the upper midwest US since Hector was a pup.

Back in the carburetor days, my son had taken my 1978 Oldsmobile to college. I had admonished him to not let the gas tank go below 1/2 full in cold weather, but I knew he wouldn’t take my advice. At any rate, one evening when the temperature was around zero degrees Farenheit, I got a telephone call. He had driven the car less than a block off campus and it quit. He called the motorclub service that I had purchased for him and had the car towed back to campus. The wrecker operator said that his fuel pump was probably shot. Well, my son didn’t have the money for that repair. I told him to go down to a store off campus and for $1 he could purchase some gas line antifreeze to pour into the tank. I suggested he wait until the temperature got above freezing to attempt to start the car. Well, he didn’t wait that long. Two days later, when the temperature hadn’t gotten above 20 degrees Farenheit, he managed to start the car. He was elated, particularly because he bought the cheaper gas line antifreeze for 49 cents. One of his classmates had the same problem and my son advised him to buy gas line antifreeze. This fellow worked in the horse stable at the college and wanted to shovel warm horse manure under the tank to warm it up. My son thought that it was worth 49 cents not to stink up the car.

In addition to the other valid information provided thus far, namely that the OP’s belief is unfounded in light of the presence of ethanol and the reality that isopropyl alcohol could damage the fuel system, there is another hole in the OP’s theory that is wide enough to drive the proverbial Mack truck through it.

Bryan–unless you have access to “industrial strength” isopropyl alcohol, you are likely using the same stuff that most of us buy in the supermarket or the drug store. Do yourself a favor and look carefully at the label. Most isopropyl alcohol is “70%” strength, and if you want to opt for the more expensive stuff, you can buy “91%” isopropyl alcohol.

Do you know what the other fluid in that bottle is?
It is WATER, to the tune of 30% by volume or 9% by volume, depending upon which variety of isopropyl you happen to buy.

So, that leads to the inevitable question:
How do you imagine that you can “prevent winter driving issues” if you are actually adding water to your gas tank?

Pure isopropyl alcohol is excellent in removing moisture from the fuel system. This is because isopropyl alcohol absorbs moisture and doesn’t phase seperate out of gasoline. Ethanol also absorbs moisture. But the problem with ethanol is that it phase seperates out of gasoline. So if you have stored gasoline with a 10% ethanol contant, and any condensation ocuurs in the storage container, the ethanol will absorb this moisture and then phase seperate out of the gasoline causing the ethanol and moisture to settle to the bottom of the storage container. which results in corrosion.

This is why you find isopropyl alcohol in products such as Iso-Heat and Seafoam.


You’re right. Hopefully, the OP is referring to Dry Gas or Heet formulations using isopropyl (not methanol).

Back in the day, when tanks were vented to the atmosphere, carbs ruled the earth and gas stations seemed less well regulated, fuel line freeze ups seemed fairly commonplace where I lived. I once had several 1-2" long icicles shoot out of my disconnected fuel line. Back then, Heet or Dry Gas were sold commonly right at the pump. With today’s closed fuel systems, fuel injection and ethanol blended gas, those additives are no longer necessary.

If gas in your area is E10, and it seems that is the most common fuel out there now, then no need to add more alcohol. There is alcohol in your gas tank already. I don’t see how adding a bit more can hurt, but why?

For years you could buy two kinds of Gas Line Antifreeze. The common less expensive products were made of methyl (methanol) alcohol. The more expensive type was made of isopropyl alcohol.

One winter back in the early 70s, I got stuck up in Montreal Canada during a cold snap (-40 overnight lows). Many were pouring rubbing alcohol into their gas tanks as a form of gas line antifreeze.

With today’s ethanol fuels, the need for gas line antifreeze is rare.

The addition of isopropyl will not prevent this separation if any appreciable amount of water is present…Ask any boat owner…

Today’s fuel systems are SEALED…They do not “breath”…Moisture can not enter the tank and condense into water…Today’s (and yesterdays) gasoline contain both propane and butane which maintain positive pressure in modern fuel tanks…Google “gasoline vapor pressure”

If you purchase gasoline from a gas station that has a low turn-around, condensation in the storage tank can occur. This condensation is absorbed by ethanol. The ethanol then phase seperates along with the moisture out of the gasoliine and settles to the bottom of the storage tank. You then fill your tank from this storage tank and now you have water contaminated gas. Depending on the conditions, this can happen in all types of gasoline storage containers. Even gas tanks on vehicles. http://fuelschool.blogspot.com/2009/02/phase-separation-in-ethanol-blended.html

Isopropyl alcohol will abosrb any moisture in the gasoline without phase seperating out of the gasoline so it can be carried off and burned in the engine.


I hate HEET and the whole gas freezing topic…I rant every single time, huge pet peeve of mine.

Gas CANNOT freeze. Gasoline has a flash point of -34 degrees farenheit, it remains in a liquid state well below this point and can spontaneously combust at any tempature down to -34. The only way you can get enough water in your gas to cause serious problems is to literally pour water into the tank via a garden hose or transfer pump. Yes condensation can build up significantly if you drive frequent short distances but even then a good road trip should burn most if not all of it off.

I’ve also heard people say that fuel injectors freeze this is also false. How does metal and plastic freeze? The reason cars have problems starting more often in the winter is due to lack of maintenance. Such as checking your battery occasionally. If you have a bad cell on your battery the cold makes the fluid in the battery contract to the point that one of your cells is pretty much eliminated thus preventing the car from starting. Not because your battery “froze.” I worked part time at a service station for five years and have gotten into many arguements who buy heet religiously.

OP I am not ripping you to shreds just the whole winter gas freezing topic at hand.

While you are definitely correct that it’s not the gasoline that is freezing, it is the condensation that causes the concern. It doesn’t take much condensation in the right places to cause frozen gas lines in freezing temps. Many of us have lived through lots of gas line freeze-ups in years-gone-by.

No disrespect JoeMario but I come from a long line of mechanics, I am a NHRA fabricator, and we have many drivers in the family and never once have we seen a gas line freeze.

I have been driving in winter conditions since my first car (a really beat-up 29 Ford Model A) as a teenager. For many years, I used dry gas type products, as cars became more sophisticated, the methanol products became harmful. Next was the isopropyl products, not so bad, but with the ethanol, not really eeded. Having said that, the ethenol holds water in suspension, so if you let your car sit unused for long periods of time, you might experience some water problems. It used to be a common practice for thrifty people to buy isopropyl alcohol in a drugstore (rubbing alcohol), don’t do that, most of these products have water in them, they are not 100% isopropyl alcohol.

“It used to be a common practice for thrifty people to buy isopropyl alcohol in a drugstore (rubbing alcohol), don’t do that, most of these products have water in them, they are not 100% isopropyl alcohol.”

Gee–I couldn’t have said it better myself.
Oh, that’s right, I did–about 5 hours ago.
Oldmotorist–please read my post from 11:59 AM.

I’ve read some of the other posters and they are correct. IPA (isopropanol) will be soluble in gas and water in it so that the water won’t freeze your lines in cold weather. With ethanol (EtOH) in the gas, it too will solubilize the water in it and the gas so it can be burned with the gas and not freeze in your lines. I wouldn’t put IPA in the gas. My question is where did you get the IPA?? please don’t tell me you’re getting it from the drug store or grocery store. That stuff for medical reasons has a lot of water in it. I don’t know if autozone (or the like) carry IPA for this purpose. I do know gas winterizer at these stores is basically methanol (MeOH) and it too dissolves the water in the gas so freezing won’t occur. I’m a chemist so I hope this and others have educated you some in this aspect. have a good day.

In days of old, gasoline was drawn from the tank by a mechanical fuel pump located at the front of the engine and fed under low pressure to the carb’s float bowl, wherein it came through a small orafice controlled by a needle valve. From there it was drawn through a small orafice in the sidewall of the venturi, where it vaporized. Matter experiences a drop in temperature when expanded, and draws heat out of everything around it. In the old systems, there were places where the fluid was moved through orafices and expanded, chilling, and any water in the system could be frozen. In addition, the fuel lines could drain back into the tank, and since water drops to the bottom of gas, moisture could remain in the lines and freeze.

Modern fuel injected systems are operated under high pressures as totally filled, closed systems all the way from the gas pump to the injectors. And when the engine is shut off, the injectors all close, keeping the system secure. There is no blowing of fuel through needle valves and orafices, there’s no opportunity for water to reside in the fuel lines (unless there’s an injector leaking, the lines will stay full of fuel just like a drinking straw stays full of soda when you seal teh top with your finger). There’s no real opportunity for icing.

And then there’s the ethanol.

And I agree that adding additional isopropyl alcohol is a bad idea. There’s even concerns with older cars about “bumping up to” 15% ethanol, just approved by the EPA as an automotive fuel, because of conserns for the seals.