The gas cars and mileages that I currently have or have had that have run Chevron Delo 400 multigrade with no catalytic converter or any other kind of problems are as follows:
'78 Ford 4X4 bought new in '77, 82K miles about 1/2 mile at a time started using Delo about 12 years ago. No catalytic converter, but no other problems.
'88 Vette bought at 70K miles, now 123K miles
'88 300E bought at 80K miles, now 199K miles
'98 4Runner bought new, 99K miles
'94 Windstar bought new 112K miles, blew head gasket at 100K, but nothing related to cat or such
Those are the gas cars that have had no oil except Delo while I owned them. In addition to this, I have about a million miles of experience with Delo in diesel cars, trucks and tractors. The top four in the above list I still own and are all in top running order.
I think that the Car and Driver comment may have come from an isolated instance where a universal grade oil was used in an engine that was burning A LOT OF OIL. If the engine is not passing oil to the combustion chamber, how could the type of oil being used have anything at all to do with anything going on in the exhaust tract?
BTW, My new C Class and my daughters new Ranger pickup are on a Mobil One diet.