Popcorn....
https://www.youtube.com/watch?v=zIvcIa-Zbvs
fridge stocked, beer in hand... Ready, set, go.....
I must confess I didn't watch it all, but I can say there is a fuel additive for large diesel engines using low ash oil which clean them up very well, the TBN for the oil analysis is way up for this stuff.
BUT
That was on big engines, 50 litre V 16's, quad turbo.
Not sure about cars.....