# Heet versus Iso-heet **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [January 16, 2023, 1:29am UTC](https://community.cartalk.com/t/heet-versus-iso-heet/188509 "2023-01-16T01:29:01Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![RandomTroll](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/randomtroll/32/12184_2.png) [@RandomTroll](https://community.cartalk.com/u/RandomTroll)\ **Post date:** [January 16, 2023, 1:29am UTC](https://community.cartalk.com/t/heet-versus-iso-heet/188509/1 "2023-01-16T01:29:01Z")
_Heet_ is methanol; _Iso-heet_ is propanol. The manual for my pickup warns me not to use too much methanol (the amount 12 ounces would add isn’t enough to matter), so I use _Iso-heet_, even though it costs $1 more. What difference does it make? ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [January 16, 2023, 1:32am UTC](https://community.cartalk.com/t/heet-versus-iso-heet/188509/2 "2023-01-16T01:32:56Z")
Heet will phase separate if water is present in the fuel. Iso-heet won’t. Tester ---
**Author:** ![melott](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/melott/32/10827_2.png) [@melott](https://community.cartalk.com/u/melott)\ **Post date:** [January 16, 2023, 1:54am UTC](https://community.cartalk.com/t/heet-versus-iso-heet/188509/3 "2023-01-16T01:54:36Z")
Also, iso is denser and will go to the bottom of the tank where water is more likely to be found. ---
**Author:** ![jtsanders](https://avatars.discourse-cdn.com/v4/letter/j/c2a13f/32.png) [@jtsanders](https://community.cartalk.com/u/jtsanders)\ **Post date:** [January 16, 2023, 4:23pm UTC](https://community.cartalk.com/t/heet-versus-iso-heet/188509/4 "2023-01-16T16:23:42Z")
2-propanol and methanol are both completely miscible in water. As for density, gasoline has a density of 0.75 g/ml, methanol has a density of 0.792 g/ml, 2-propanol density is 0.786 g/ml, ethanol density is 0.789 g/ml and water density is 1g/cc. All three alcohols are pretty close in density. If they do sink to the bottom, that’s good and will help scavenge any water present. Once the car is moving it all gets mixed up quickly. ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [January 16, 2023, 4:51pm UTC](https://community.cartalk.com/t/heet-versus-iso-heet/188509/5 "2023-01-16T16:51:29Z")
> **[Paul Brand: Fuel line antifreeze not all hype](https://www.startribune.com/fuel-line-antifreeze-not-all-hype/36707014/)** > > Q Isn't using a gas line antifreeze these days ridiculous? All our "oxygenated" gasolines are at least 10 percent alcohol already. Tester ---
**Author:** ![jtsanders](https://avatars.discourse-cdn.com/v4/letter/j/c2a13f/32.png) [@jtsanders](https://community.cartalk.com/u/jtsanders)\ **Post date:** [January 16, 2023, 5:40pm UTC](https://community.cartalk.com/t/heet-versus-iso-heet/188509/6 "2023-01-16T17:40:34Z")
The article you posted adds that 2-propanol sinking is a function of its combination with water, and did not differentiate between Heet and Isoheet except to say that methanol may damage rubber and other plastic components. Ethanol will do that too. ---
**Author:** ![RandomTroll](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/randomtroll/32/12184_2.png) [@RandomTroll](https://community.cartalk.com/u/RandomTroll)\ **Post date:** [January 17, 2023, 4:27am UTC](https://community.cartalk.com/t/heet-versus-iso-heet/188509/7 "2023-01-17T04:27:31Z")
I have to pass the emissions test before March 1. I last bought gas 2022 January 22. It may be waving a dead chicken, but it’s worth it to me to put in a bottle of _Iso-heet_ and gas treatment, as well as spray a lot of carburetor cleaner on the carburetor beforehand. My memory of the fuel additives was that they wanted you to add them just before fueling. That seems to have changed, but it’s my habit. That should mix them.