Can I mix Sea Foam and Iso-Heet in a gas tank?

Great question Sam. Yes, you can mix Sea Foam and Iso-Heet. Both will mix evenly with each other and   will disburse evenly in the tank fuel. They also work well together as cleaners.

Can I mix HEET water remover with Lucas Upper Cylinder Lubricant during the SAME fuel tank fill up?

Hi Rick. You will have to ask Lucas. If you meant to ask about a Sea Foam product the answer is yes, you can mix Iso-HEET with any Sea Foam fuel treatment product!