AO Gold Member
Join Date: May 2008
Location: United Kingdom
County: Perth and Kinross
Whenever I've asked the engine-flush question, the answer has been no...although there has been one time when I have used it on a very emulsified engine!
If you want to give it a good clean, give it a fill with cheap oil and filter, drive it for a few hundred miles, then change it for the good stuff.
There are two distinct types of coolant. You need to make sure you don't add one to the other, or it'll turn into a sticky mess! If in doubt, flush it out!