The fleet speed was about 15 knots, ships would not tear around at flank (18 for the KE's 21 for most DNs) due to the wear and tear on machinery, crew (stoaking coal boilers is a beotch) and ofcourse, fuel consumption.
The RN used oil on two classes, the Royal soverigns and Queen Elizabeths, every other Dreadnought was coal fired. The Renown class was also oil fired too.
These were all late generation Dreadnoughts, the last ones built by the RN.