Like everyone has said, I've heard bad things about Motor Up as well.
What I DO recommend, is STP Engine Flush.
Buy some, pour it in your oil and let it run for about 15 mins. In an already WARM engine.
Keep the RPM up around the 2k mark and do NOT go driving with it in your engine.
15 mins later, drain the oil. When I drained it, there were big thick BLOBS of oil that came out! Nasty!
Chuck in some new, good quality stuff, change the oil filter and for best results, repeat after 6-7k km's.
About comin' up time for me to do it again, chucking in some Amsoil this time
Motorsport is like sex. You could take it to track and have a long, enjoyable session, or you could take it to the strip and get it over with in less than 20 seconds.