Yes adding HEET fuel additive to your gas can cause the engine to run rough.
If you add too much HEET to the gasoline then it can make the engine run rough but when you add the proper amount of HEET to the gas tank the engine should not run rough.
If you only have a half of tank of gasoline and add a full bottle of HEET to the gas then it could cause the engine to run rough.
A rough running engine can be caused by bad spark plugs, bad EGR valve, bad fuel injectors, clogged fuel injectors, clogged fuel filter, low fuel pressure, bad ignition coils or even bad gas.
Putting HEET in your gas tank after every other fill up is a good thing.
The HEET helps to mix with the gas and keep the water and moisture out of your gas tank as water and even tiny water droplets in your gas can cause issues with your engine.
A full bottle of HEET fuel additive can help treat a full gas tank full of gasoline.
I always add a bottle of HEET fuel additive to my gas tank especially in the winter months or when there's a lot of rain.
Just don't put too much HEET in your fuel as it can cause the engine to run rough and even stall out.
But when adding the proper amount of HEET to the fuel the engine should run better.
Yes you should put Heet fuel additive into your gas tank at every other fill up or every fill up during the winter months when it's cold.
The Heet helps remove any moisture and water from the gas that gets into the gas tank naturally which prevents the fuel lines from freezing up.
The Heet that removes the water droplets helps to also prevent problems with your car stuttering and stalling.
I use Heet fuel additive every fill up during cold weather and it does help a lot.
It's not all that expensive and prevents problems if you're living in a cold climate.
Also if you let your vehicle sit for awhile such as longer than a few weeks then put some Heet into the gas tank to avoid water and moisture from getting into your fuel system.