Even if you are a great fireman, oil burning locomotives always have more firebox issues. It all comes from the expansion and contraction imparted by the fire. Whereas a coal fire heats up and cools down rather slowly, an oil fire always is in step with what work the locomotive is doing. You can go from a nice spot fire, to a wide open charge in seconds, and the fire has to keep up. Railroads with roller-coaster profiles are tough on fireboxes, and the firing is constantly being changed. You can't really let the fire go up and down slowly without making big clouds of black smoke with you have too much oil and no draft, or even worse, slowly bringing up the fire when the throttle is ripped open, or you run the risk of getting your fire sucked out and lots of cold air being drawn into the firebox. The corners of the firebox is where the damage is concentrated, with the side and end sheets of the firebox constantly expanding and contracting. All the stress is placed in the corners.
The Texas State RR was one of those roll coaster rides. There was never a time when you weren't doing something. or getting ready for the next "something". The departure from Rusk made me cringe every morning. It was all down hill from the engine house to the depot. Once the engine got rolling, you rode the engine brake all the way to the depot, where the train had been set out the day before. You needed a tiny bit of steam to back to the train. Upon departure, you kicked the independent air off and let her roll, used the automatic to make a rolling air test, held on to the set to stretch the train, then at the bottom of the hill by the dam outlet, you released the air and ripped the throttle wide open for a short, steep 2% charge up the hill. The firebox was still pretty cold, the bricks weren't hot yet, you had no choice, but to crank the oil up, turn up the atomizer and hang on. The superheater wasn't hot yet, so the locomotive was essentially a soak, devouring water at an amazing rate. Even with a heavy fire, the cold bricks made it just possible to hold your steam pressure. In a couple of hundred yards, the grade eased a bit. By then bricks were warming up. The hogger hooked her up a bit, the steam started up, you started the injector, to replace all the water that just got sucked out of her. Then he backed out into the first of a dozen sags. By now the boiler had "thawed out" and was steaming like it should. But I could just imagine the corners of the firebox screaming every day, as the side and end sheets of the firebox rapidly expanded and contracted through all that....
