Sentence:  In the early years it["Top Gear"] had been very much a series for people I believe are known by the curiously unappealing term ‘<WSD>petrolheads</WSD>'. Since most <WSD>petrolheads</WSD> are probably out in the evenings, burning up the rubber or the tarmac or whatever it is that <WSD>petrolheads</WSD> do, the show had a fairly limited audience. 
Meaning of the word marked with <WSD> tags:  A car enthusiast.