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I've been worried about my '03 Ranger ever since I looked at coolant water temperature (cWT) on the scan gauge. It has been returning temps of 250-260F when climbing hills. After researching this, it appears that what the ECU is reporting to the scan gauge is cylinder head temperature (CHT) rather than cWT (which stays in the middle of the dash gauge on hills). From what I've read the engine should throw an error code and shut itself down if CHT hit 270F.

I'm interested in grille blocking in the cooler months, but I don't know what CHT range I should shoot for. Does anyone here have any thoughts about what the safe and efficient CHT ranges are?

I don't think that 270F is excessive for a cylinder head temp, but it is pretty high for coolant temp. I don't think the scan gauge is reporting CHT. The Ranger may be calculating ECT from a CHT reading, however. Try using the CMNDS feature on your scangauge to retrieve the CHT and ECT values. Hopefully the PIDs are the same for the Ranger as for the FEH. Coolant temp is 1139, CHT is 1624. ECT is in degrees F with a scaling of 2, while CHT is in degrees C with no scaling.