Reader Question: Ethyl vs. Isopropyl Alcohol?

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Here’s the latest reader question, along with my reply!

Jon asks: Love your site, love your writing. My question is, is ethyl-alcohol as hydrophilic as isopropyl alcohol? That is, will the ethanol in our gas “carry” the condensation in our tanks and lines into the combustion chamber, as dry-gas does? If so, should we still periodically run a bottle of dry-gas through our fuel system? Thanks, Eric; keep up the good fight.

My reply: First, some definitions – and I’m winging this a little, so if I’m in error hopefully someone will step in. Okay, my understanding is that isopropyl alcohol is ethanol (generally about 70 percent) but “denatured” via the addition of what are called bitterants, which make it poisonous if consumed. The stuff is used as a topical disinfectant.

Drygas (it’s a brand-name) is contains isopropyl alcohol and (sometimes) methanol; the purpose was to prevent water in the gas from freezing in the fuel lines/causing similar problems. The alcohol/methanol absorbs water in the fuel – so it doesn’t separate out – and the mix in solution is then circulated through the fuel system and eventually (harmlessly) burned.

The degree of water-attractiveness would likely depend on the percentage of isopropyl alcohol in the mix. Given that most bottle-bought isopropyl is 70 percent ethanol (denatured) while most unleaded regular sold in this country is 10 percent ethanol, isopropyl would appear to be more water-attractive than the ethanol-laced gas and so more effective at ridding your gas tank/fuel system of any excess of accumulated water that has separated out.

Of course, the small bottle (just a few ounces) of 70 percent isopropyl will be spread out over however many gallons of fuel are in the tank.

That said, it certainly can’t hurt to run a bottle of Drygas through the system every now and then – more often in winter, when the tendency for condensation (and separation) to occur is greater. The cost is negligible (less than $5 a bottle) and there is zero downside, so far as I am aware.

Supposedly, late model cars with tightly sealed fuel systems (i.e., vapor recovery/evap emissions) are much less vulnerable to condensation formation arising from external sources. However, the ethanol-laced “gas” is itself likely to carry some water along for the ride and while it may be held in solution by the ethanol and harmlessly consumed, it may not be.

Given how cheap Drygas is – and the potential benefits vs. the nonexistent risks – I’d add a bottle once every six months or even once every three!

. . .

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  1. Sorry Eric, iso-Propyl Alcohol (Isopropanol) is a different molecule from Ethyl Alcohol (Ethanol). The alcohols start with Methyl (Wood Alky, very poisonous, CH3OH) with one methyl group (CH3) and one hydroxl (OH), and go up from there with the number of methyl groups. Ethanol is C2H5OH (not poisonous in reasonable quantities), Propanol is C3H7OH (poisonous again). The “iso” bit tells where and how the hydroxl group is attached to the rest of the molecule (the molecule’s arrangement, as it were). Methanol can be one of the “denaturants” used to make Ethanol toxic, and therefore undrinkable, there are others. Ethanol is, of course, the stuff in any good Scotch Whiskey that makes you happy.

    You know Methane (Natural Gas), Propane, Butane, etc.? The naming convention is the same for alcohols, Methyl Alcohol, Ethyl, Propyl, Butyl, etc. like Methane, Ethane, Propane, etc.

    HEET/Drygas is either Methanol, or iso-Propanol (“Iso-HEET”). Either one seems to be good at absorbing water and keeping it in solution. Ethanol is not as good, and I’m not 100% sure why.

      • Oh hell yes. Takes more energy from seed to tank for a gallon of hoochanol than a gallon of dino squeezins, so it really makes no sense. Send that corn to Kentucky so the good distillers there can make good Kentucky Boutbon Whiskey of it, please!


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