well,
I think it doesn´t matter what brand of "engine flush" you use, as long as this product fulfills important points:
1) should be designed for Motorcycles (the car stuff can be way to aggressive and harm your seals)
2) the producer must guarantee that his product is making micro-particles out of the "internal dirt". If he can´t guarantee this,
big particles will be removed and can clock all your oil-lines... Done this do a car, I´d actually takes a while until you recognize
tthat your oil-lines are clocked...
Anyway, where I do live the Castrol stuff isn´t available - I use Motul Engine Clean Moto, a sit fulfills all the requirements above-
hope this helps?
peter