A steam locomotive is known to be able to pull more then any pure combustion engine locomotive. (Uncited)
Why didn’t oil fired steam locomotives take off?
This started when I watched: https://www.youtube.com/watch?v=Hszu80NJ438
During the runtime, it mentioned oil fired retrofits.
I search it up, and found one.
It was an overview video of a modern retrofit, and it seems to not be too difficult to retrofit, even using the same steam blaster to spread the oil in the smoke box: https://www.youtube.com/watch?v=Up1UaMVnv4M
Oil burning was common in some regions. The Southern Pacific had a lot of oil-fired engines. Their famous “cab-forward” steam engines could only make sense as oil burners without fundamental redesign.
Part of it might be that the last holdouts for steam, who made the most technically advanced engines, were predominantly coal-carriers. They didn’t have the oil infrastructure, and didn’t want to burn relations eith their customers.