I have a 252 that runs well, but I notice that it requires a lot more throttle than my post war trains, I was just curious if this is common or not.  For example, when running something like a 2343, I can pull 6 cars and a dummy with the ZW set at 8, but to run this 153, I need to set it at about 14 when pulling 3 cars, or about 10 to 12 by itself.  Doesn't appear to be straining at all, and doesn't seem to get too terribly hot, nothing that would damage it at least.  I generally only run older engines like this for short periods just to go easy on them with time to cool between anyway.