Context: Asphalt/bitumen is typically stored and transported at temperatures around 150 °C (302 °F). Sometimes diesel oil or kerosene are mixed in before shipping to retain liquidity; upon delivery, these lighter materials are separated out of the mixture. This mixture is often called "bitumen feedstock", or BFS. Some dump trucks route the hot engine exhaust through pipes in the dump body to keep the material warm. The backs of tippers carrying asphalt/bitumen, as well as some handling equipment, are also commonly sprayed with a releasing agent before filling to aid release. Diesel oil is no longer used as a release agent due to environmental concerns.

Question: About what temperature is asphalt shipped?
Answer: 150 °C

Question: To promote what characteristic is diesel oil added to asphalt for shipping?
Answer: liquidity

Question: What is the liquefied mixture called? 
Answer: bitumen feedstock

Question: What truck feature is occasionally used to keep asphalt warm?
Answer: engine exhaust

Question: Due to what concerns is diesel fuel no longer used as a release agent for transporting asphalt?
Answer: environmental

Question: To retain liquidity, what is sometimes mixed in with engine exhaust?
Answer: Unanswerable

Question: Diesel oil or kerosene is often mixed into what to retain warmth? 
Answer: Unanswerable

Question: Due to what kind of concerns is diesel oil now used as a release agent?
Answer: Unanswerable

Question: Environmental concerns are the reason engine exhaust is no longer used as what?
Answer: Unanswerable