I have an old British Eagle MTB with 18 speed Shimano Uniglide. I have two questions; The chain (KMC) is approx. 4 years old and has been regularly cleaned and oiled in situ. I have measured the chain and it has no stretch yet. I would like to take the chain off and soak it in some kind of solvent to really clean the chain. What is recommended - petrol? Some kind of degreaser? What should I rinse it with after using solvent/degreaser? Re. the two small plastic jockey/idler wheels on rear derailleur (not sure what they're called) - last time I had these off, I greased the inside of the wheels with standard Castrol LM grease. I'm going to remove them, clean and re-grease. Is the Castrol ok, or should I be using something different? Also, how long do these wheels last? Mine are original and best part of 30 years old. Are new ones for my bike available? Thanks for any advice and help.