Hanso, I've always wondered about the safety of using a flushing product, have you always had good results with it? Also would it be safe to use STP injector cleaner?
I recently had an oil and filter change and the mechanic used exactly 5.5 litres which filled to the top mark. He used the same method, took all plugs out and let drain for a fair while.
I just use Motul 3100 20w50 cos I change every 3000 kms and can't justify the expense of full syn. here in Brazil. Motul 3100 (22 Reais or 11,50 dollars) Motul 5100 (38 Reais or 19,80 dollars) and that's with a strong exchange rate.
Cheers