Merlin III
Amendment List No. 4 from November 1940 of AP 1590B Merlin II and III Aero-Engines has the following limits:
Oil
Type ... Specification D.T.D.109
Inlet oil temperatures
Minimum for opening up ... 15°C
Maximum for continious cruising ... 90° C.
Maximum for climbing or 30 minute emergency (1 engine stopped : multi-engined aeroplanes) ... 90° C.
Emergency maximum (5 minute limit) ... 95° C.
Coolant
Type ... Treated ethylene glycol: Specification D.T.D.344
Outlet temperatures
Minimum for opening up ... 60° C.
Maximum for cruising ... 95° C.
Maximum for climbing and level flight (5 minutes limit) ... 120° C.
Maximum for 1/2 hour emergency* ... 120° C.
* Though not stated, I assume this limit is for multi-engined aeroplanes with one engine stopped, because there is no 30 minute emergency for single-engined aeroplanes.
The initial limits (without amendment) stated in AP 1590B Merlin II and III Aero-Engines (October 1938, reprint October 1939) are the same.
However, IIRC the Pilot's Notes Spitfire I of the Collector's Edition state higher limits.
Merlin XII
The Merlin XII employs a mixture of ethylene glycol and water instead of pure ethylene glycol.
The Pilot's Notes here:
http://www.scribd.com/doc/4598146/Pi...lin-XII-Engine
state 120° C and 95° C for emergency (last page).
However I know that there are 2 different versions of Pilot's Notes Spitfire IIA circulating, for example this one:
http://www.scribd.com/doc/46069063/1...e-II-Aeroplane which states the 135° C and 105° C.
Conclusion
There are obviously different limit depending on the date of the publication. My conclusion is that the limits for Merlin III and Merlin XII were changed over the time. We have to take a close look at the Amendment Lists for every publication.