You put water wetter in the expansion tank. I honestly believe it does not do much. Antifreeze already has surfactants and corrosion inhibitors in it. It will also form a scummy oil layer in your expansion tank when cold.

 

x2 for being a fan of very few additives. Not a fan of water wetter and definitely not a fan of any viscosity modifiers in lubricants, like Lucas. The only exceptions for me are additives formulated to solve a specific shortcoming with standard products in a specific application.

For example, there is an additive called Camguard I use in an aircraft because it was developed by a friend who ran Exxon's lubrication engineering department for many years and is designed to enhance the residual film properties on camshafts in engines which fly infrequently to protect against corrosion, and was specifically engineered to not alter the lubricating or viscosity properties of the oil itself.

In using most automotive additives, I would be putting myself in the position of lubrication engineer, somehow sure that the engineers at Mobil or Prestone were ignorant and forgot to put something in...or intentionally left something out...and that a bottle of elixer xyz will put it back. Are any of us qualified to make that decision? Do we know for certain it's not going to do more harm than good in the long long term? How does Water Wetter affect nitrile hoses? Does it react at all with the solder in the heater core? Will it affect the lubricating properties of the coolant formulation on the water pump at all? Does it become corrosive if it's exposed to combustion byproducts?

Good marketing sold snake oil and cure all pills for centuries. The same thing happens today. I leave the lubrication and cooling system chemical engineering to the pros, and I run what the manufacturer recommends and keep it clean.

Dave