It's the artificial ovoids I've been using on my open fire at home for years, they're great on my fire but the results are very variable on steam locos, it's a totally different firing technique that some have struggled to adapt to.
It's not just passengers who are struggling with rising living costs, volunteers are in the same boat, I can think of a number who have cut their turns from 4 a month to 2 a month because of fuel costs and it may yet get worse. The Wensleydale has had to cancel some days operation this year because of a lack of volunteers (sourced from their official facebook page) and I think some other railways have had to scale back things like shop opening or booking office hours for similar reasons.
It still blows my mind though that some preserved railways still can't get the basics right though, clean and warm trains aren't a big ask most of the time, getting the whole customer experience (yes I hate the term too) right is more important than ever now and too many places still haven't realised it!