No – they burn very cleanly.
The globes need a wipe occasionally if you’re fussy – fingerprints and dust mostly, not carbon or anything.
the flame burns a bit yellow at first, but settles down within a minute or two as it gets warmed up.
the stoves and lamps have a needle valve which can get blocked up – we used to clean these maybe once a year? But thats with the lamps getting completely abused by an entire scout group – even if you were camping regularly, you’d maybe have to do this once every few years.
I’ve only ever run them on unleaded
As I said – the lamps aren’t for everybody 😀 but the Coleman stoves definitely ARE…… and if you are running the stove already, using the lamps too kinda make sense.