 They carried 3 @,@ 500 long tons ( 3 @,@ 556 t ) of coal , and an additional 1 @,@ 135 long tons ( 1 @,@ 153 t ) of fuel oil that was to be sprayed on the coal to increase its burn rate . At full capacity , they could steam for 5 @,@ 610 nautical miles ( 10 @,@ 390 km ; 6 @,@ 460 mi ) at a speed of 10 knots ( 19 km / h ; 12 mph ) . 
