I have only ever used Tesco's because I have their credit card/clubcard. Smokes quite a bit but does reasonable mpg.
Had to use BP on a couple of occasions and it has felt better (might be psychlogical) but still smoked.
LOL Just spent all afternoon sorting out the stuck tensioner arm and noisy pulleys etc
Wish I had done this to mine before it snapped the tensioner off!!!! 
didnt appear to have anything really wrong with it,l me and the boy swapped the lower pulley yesterday as mine had a grumbly bearing, but the clue was when i switched off there was a horrible creaking noise as it stopped, If i put tension on the belt by pushing it hard in the long run i could recreate the creaking noise, so i pulled it all apart today to check, shimmed up the play in the tensioner stripped and regreased the arm on its spindle(was jammed with spanish dust that had turned to concrete)
stripped the dust covers off the pulleys and regreased the bearings,
fitted new water pump(steel impellor of course purely because i had it )
And this bit will please the boy!! it got to dark to refit the viscous fan!!!
so its going to run next week without it!! the creak is no longer there the engine is definetly quieter and now it just switches off with no nasty or strange noises!!Havent driven it yet as was to cold when i finished but ran it up for half an hour before i got into a steaming hot bath 
As your viscous works, remember to store it upright at all times, but I'm sure you know that.
Will be interesting if your engine now gets up to temp better - you saw mine runs bang on 95C all the time (on the guage).
Might be worth considering changing stat if its still a little cold :-/ (10 min job if no viscous on

- though need to retop and bleed coolant obviously)