Air filters got dirty real quick. It's a big factor for long hauls in dry areas.
Our neighbor had a mid-70s Cat D6 just sitting in his field for years. Engine was seized solid. A few of us from the shop would talk about it over coffee. Finally got a weekend free and we all just showed up with tools. Took the head off, soaked the pistons, worked them loose over two days. Got the injectors cleaned up and put it all back together. Fired up this morning, first crank. Sounds rough but it runs. Just feels good to see an old machine breathe again, you know?