Cummins x15 fuel tank heater

Hi all, I've this International HX520 with x15 that has fuel tank heaters which are supposed to keep the fuel in the tanks warm while the engine is running. I recently installed an Espar hydronic coolant heater to keep the engine warm in those brutal winter nights when engine is shut. What I'm wondering about is whether the coolant going trough the fuel tank heaters is plumbed to the same coolant cycle that the espar heater is connected to and will running the espar will warm the fuel too. I don't idle up until the temp drops below 25 and I never experienced any issues in the past using webast coolant heater and good fuel additive. What I'm trying to determine is whether the fuel tank heaters will be enough to go through the winter, or I should keep adding fuel antigel with every stop at the pump. I know that 10 bucks on top of every tank is nothing compared to a tow and shop bill for a frozen truck and I'm not planning to completely stop using additive, but with the current fuel prices it's vital to save every $ possible to maximize profit.