Just because its the latest oil doesn't mean its better. The latest Delo 400, the Delo 400 LE is Low Emissions, and some of the Berg 'goodness' is removed accordingly. OTTOMH it has less sulphur, which is good for roller/ball bearings and gears, which I'm led to believe is good for impact loads. Lots of modern oils are designed for plain bearings where film strength is a priority, but they don't work as well with roller/ball bearings and gearboxes. I believe my 501 experience where I changed the roller followers and damaged camshaft after running exclusively on Mobil 1 4T to new parts and also changed to Delo 400 at the same time have confirmed it to me. I have over twice the hours on the motor now than previously, and no sign of a problem. The log book is a bit scratchy, but now approximately 33,500 kms total. Did the above switch at about 10,000 kms. At 5,000 kms the crank was done as a precaution and probaly not needed based on subsequent experience, new valve seats were fitted after the inlets disintegrated and a Wiseco piston. Not touched otherwise mechanically. Externally, an FCR and a few stators have also been done and some patching up of the exhaust.
Steve