I did try the R candles many years ago and the result was black acrid smoke!!!! I have a 5 litres Of R down the shed and often mix a teaspoon full in with juice of My lawn mower smells very speedway Have done the same trick with the XS and Bandit smells nice but like you say gums stuff up.But I only use a tea spoon in a full tank just enough to get the air scented, As for brake fluid I have not had the same result I have tried it but I think it as to be castor based.Unsure of the chemisty did not smell like R though. My Dad ran his Triumph Mettise 500 on Castrol R untill he locked the motor up going though a river at the ISDT he then had to wash the motor (bent the rods) to remove all the R so he could go back to normal grade as the two don't mix at all.