What types of fuels are approved for Oil-Fired SEE Portable Heaters? The approved fuels are: No. 1 and No. 2 fuel oil No. 1 and No. 2 diesel fuel JP8/Jet A fuel Other Frequently Asked Questions About Portable Heaters: Can SEE heaters be used indoors? How do I size a space heater? What type of heater is better, one that runs on Fuel Oil or LP? Do all portable heaters require electricity?