4cyl car started firing on 3 cylinders, I was out in the countryside and couldn’t do anything about it.
Drove home for about 5-10 miles at as low revs as possible, changed plug and lead and now its fine.
I did not unplug the injector on the bad cylinder for the 5-10 mile drive (impossible to reach without tools).
I have since done an oil change, nothing offensive in the oil.
How likely is it that I’ve fuel washed the offending cylinder and damaged it in some way with this short drive?
10 miles at low speed, it’s not very likely that you have done any serious damage. I have seen engines that were fine after missfire for over a thousand miles.