The following excerpt is taken from the AFV(T) Mediterranean Area Technical Report No.26, dated February 26th, 1945.
The average life of the engine in one unit is 225 hours, which is equivalent to about 900 miles. Some engines have done 300 hours. In no case has the unit removed an engine from the vehicle and carried out a proper 100 hour overhaul, but they have done all that can be achieved with the engine in situ. It has been pointed out that the proper 100 hour check is of the greatest importance and would definitely lead to a longer engine life. With this the unit agreed, but said that the time was never allowed for them for such a procedure. From visits paid to other Priest and Sherman regiments, this seems a general complaint."
These numbers are fairly interesting, since they can be compared with the mad dash for Berlin on the other side of the front. There, T-34s were racking up 2000-2500 km and 250-300 hours without overhauls. Mere days after this decree, the minimum (not average) lifespan of T-34 engines was increased to 250 hours.