Rodger...

The #251 never ran with the side-tanks on her, whereas the 250 kept them for approximately six months before they were taken off. I'm pretty sure the tanks weren't used on the 250 since in the photos I've studied from when she had the tanks as well as the tender, the tank hoses seem to run from the tender to the injectors. The thing was that the 251 evidentally needed an overhaul before she could run, so she went in the shop for a complete overhaul before entering service. The 250 on the other hand was in pretty good shape, so they just did the necessary stuff to covert her to an oil burner and added the tender. In one picture she has her tender, is numbered 250 on her cab, has a masked #50 on her sidetank, and her headlight still has 50 on her numberboard. She also hasn't recieved her cross-compound pump yet. So I have surmised that with the 250 the attitude was kind of, "Well, let's get her out on the road and take care of those tanks and other little things later." She entered service three months before the 251. If you can get your hands on a copy of the 2005 Narrow Gauge Issue of Finescale Railroader you might enjoy it as I was able to put together an article about the mallets during their stay on the S.V.Ry.