My mate used it on his 1938 Morris, left it for 24 hrs and it worked. He said to use the full fat genuine stuff. He was on the fence about it until he tried it.@Tupers try Coca-Cola to un-cease the pistons, no seriously, apparently it works, you've nothing to lose.
Sounds mad, but I've had results from the 'black doctor' before. Personally would drink it though.