The cost of Diesel fuel at Texas gas stations $2.86 to 3.45 a gallon. So that's what to use in your Diesel heater!
http://www.bostongasprices.com/GasPriceSearch.aspx
Sounds like a big building. If it's got a real high ceiling, heating with a Chinese heater might be slow. My basement shop is small (22x15?) with a low ceiling of uninsulated main level flooring. The basement floor is a cool slab at ground water temps (I try to stand on insulation foam floor mats). The air warms up pretty fast. Even when the tops of Concrete Walls are around 35F. The windows are leaky too! It would be a lot of trouble to insulate this shop. Not gonna happen.