Avoid products that claim you need more during the cold and less when it warms up. Although they may have some positive effects they usually claim to treat a significant amount of fuel on the front label , but when you read the fine print you see they treat a lot less than you thought. Buying an additive can be complicated enough without these companies confusing us even more while trying to make a fast buck. You should also avoid products that contain alcohol's or solvents. They can cause many negative side effects, and because of all the bad press alcohol has gotten recently many additive manufacturers are trying to hide the fact if they contain alcohol.
Alcohol is usually very easy to spot just by the smell.
Alcohol is used in the majority of additives not because they work so well but simply because they are cheap to manufacture. You may consider an antigel that contains other properties such as a water dispersant, cleaning agents, fungicide and a lubricant but again ask to see documentation of these claims. You can write or call a company and if they cannot provide you with independent test results don't buy there product. Understanding all of the different cold weather terminology can be difficult as well as misleading. Many people think this is a blended fuel and it is not.