Have never used Kreen before, but I do own a 98 V70 T5, with 177,000mi on her. Wondering how it got so sludged up? Noticed your tag 'the motor is in pieces'. Are you rebuilding?
I've used BG109 before to clean out the motor when a faulty vac line in the PCV system caused the oil to quickly turn black and reak of gas. Did an excellent job. With 109 though, you pour it into a hot engine, open the hood, increase idle to about 1500 rpm and run it for about 20 min. then immediately drain. In other words, you don't drive it with 109 in it as it kills the viscosity. Kreen can be used while driving from what others have posted here.