Fired thermal oil heaters require a gaseous or liquid fuel to produce heat, finding ways to reduce fuel usage or use alternative fuels are of interest. Is the fuel you plan to use in your system a commonly purchased commodity? If fuel is purchased, heater efficiency should be a primary consideration when investing in a thermal oil heater. Generally, more surface area will yield a more efficient model, but other options are available. Preheating the combustion air for the burner is one way to boost a heater’s efficiency and save fuel. Another is to operate the system at a lower temperature when possible. In systems with multiple heaters, setting up a lead-lag computer PLC system to strategically fire each heater optimally will both reduce cycling and save fuel. Another option is sourcing “free” fuel that normally would not be used – or even considered – as a source of heat. It is quite common to encounter waste fuels being burned in thermal fluid heaters by direct firing, or by blending with commercially sold fuels such as No. 2 oil or natural gas. Most burners can be set up with appropriate controls to safely and efficiently burn common waste fuels such as heavy oil, vent gas and other combustible byproducts of chemical processing with sensible heating values.