I was out all day yesterday, and did not look at the puzzle until I was on the train home. Burning the midnight oil I did most, and have now finished it. When I looked at the Forum, all the queries related to clues I had no problem with. However, the one I can't parse is 19 across. Is the fourth letter I or O? The reference to fuel seems to lead to I, although there is no inidication of an anagram, which is needed to fit it in. Also spelling, the number of Ss, is confusing.
Clarification, please.