[No Solid Fuel Vehicles] Startup setting 'nsfv-maraxsis-diesel-submarine-fuel-categories' references missing fuel categories: maraxsis-diesel. Applied valid categories: light-oil, rocket-fuel.

Happens with:
https://mods.factorio.com/mod/rocket_fuel_is_now_fluid

Also tried removing rocket fuel as valid option in the settings, but it still gives the error, the car does accept fuel though

If i deactivate rocket fuel is fluid mod, but leave diesel engine active, i still get the warning.

Thanks for the report!

I guess you don't have Planet Maraxsis installed. But my mod still checked for its maraxsis-diesel fuel category. I've fixed it now