2005 Porsche Boxster 2.7L 5-spd manual. Recently purchased with the previous owner using LM 5W-40 of some type. This being my first Porsche H6 I didn't think much of the valvetrain clatter I was hearing, figured it was normal. The car is only driven during the warmer months and stored in an attached garage that never gets below 40F in the winter, so I wanted to try a 15W-40. Noticed an immediate difference- the valvetrain became much quieter and the engine felt much smoother across the rev range, much more enjoyable to open it up like it was designed to be driven. Refilled with Rotella T4 15W-40 and will sample again next year. Still has the original IMS bearing and although the numbers look good it will be changed next year.