For most of the time, the railway's steam locomotives have burnt coal . The requirement for the locomotives to have a hot fire burning efficiently for a solid hour has led to problems when best Welsh steam coal has not been readily available. During 1978 Nos. 2 and 8 ran with oil burners . To hold the fuel oil , a tank was fitted to the roof of each locomotive. The tanks were thin and followed the profile of the roof. In 2000, No. 2 was again fitted with an oil burner in an attempt avoid the increasing problems of obtaining suitable coal.