I've been using the Motul 5W-40 for something like 35K miles. It's expensive, but when you're changing the oil yourself, the total cost winds up being the same. I was about to switch to the M-1 T&SUV because of all the raves about that, but now that's cancelled...I'll be sticking with the Motul. The Delvac is a diesel formulation (?), OK for the catalytic converter?
On Mobil 1 10w-30 I'd burn about half a quart every 5K, with the Motul it's only burning about 1/10th a quart every 5K, with 107K on the engine.
I've sent the oil to Blackstone a few times and they always give it a thumbs-up. Initially they said I could easily take it to 7.5K between changes, but now they seem to be on the 5K bandwagon for this car. The last time I had a TBN done, they said it could have left it in until 5.5K.