For one thing, the sulfur in earlier diesel inhibited microbial growth. Also, the higher level of performance-enhancing additives in today's fuel gives the bugs more food sources. Other additives that emulsify water and diesel spread microbes more thoroughly through the tank. Mr. Chesneau is not the only one who sees a threat. Recent reports in fuel trade publications characterized bug contamination as an occasional, industrywide problem that may have been worsened by the introduction low-sulfur diesel.
Heating oil is similar to diesel and comes from the same distillate stocks.
There is some deterioration of the fuel. Others in the petroleum industry disagree that the situation has worsened. Those problems can technically occur, but that is why there are additives. We haven't had a single complaint about this. Mr. Chesneau recommends that fleets maintain continuous fuel surveillance by routinely taking samples from tank bottoms or from fuel filters.