I use them cans of engine cleaner from halfords.
What i do is... when its time for a oil change. drive to halfords. the engine and oil will be up to temp by then. buy the flush and filter. put the flush into the engine in the car park then drive home. I dont strain the engine but dont drive like a granny either.
then when i get home i put it stright on the ramps and dump the oil when its still very hot.
I do this on my bikes and car and can tell you they are spotless inside. no damage or wear from it at all.
lol i used to do the exact same thing!!!!!!
Ming