I think a flush is really important and even necessary sometimes, but there are some who say that they would rather leave all the crap inside the engine preferring not to "dislodge" it from the side walls of the internal engine area.
Firstly, if any "sludge" fell off the inside walls of the engine it would fall into the sump, if somehow it would then manage to get sucked up into the engine oil the ways it would have to get trough to the really fine mesh that is on the bottom of the oil scavenge pick up filter (doubtful - if not impossible) but supposing it managed to get through the fine mesh on the pick up, it would then travel directly to the oil filter (that is what it is for) and there is NO WAY any crud can get through a paper centred oil filter, it isnt possible so lets not even go there.
So I dont listen to those that say "I would rather not in case it dislodged some crud on the inside of the engine".
The ONLY downside to having a engine flush is the cost and if you do it yourself then it's minimal to say the least.
Some say, They don't want their 1.8T "flush" going through their turbo's, it may damage them.
This is a fair point, but not a good one, We all know that the turbo's dont spool up until the engine gets to about 1500 -2000 RPM, and I DO NOT rev the engine up when on a flush, I always let the enigne run for 30 to 40 minutes on TICKOVER, I do not reccomend that you drive the car or rev it above 1500rpm whilst flushing.
