These engines like high revs with no damage normally occurring, i would say best to shift about 3000 rpm if you want economy ...
Some people say sludging can be caused by using low octane fuel so try and run it on as high as you can obtain for where you live but dont add octane addatives as these cause all sorts of running problems with the cars ecu etc.
Also most important keep oil changes done reguarly and try and give the car a good run at speed a couple oftimes a month to blow out the carbon build up accumilated on the short 2 mile runs ..
