The Synthetic Diesel Oil does in fact have the additional additives. And a much better viscosity range for a stock car compared to the 15w-50. Here's a comparison of some of the options. I don't see any reason to rule out the synthetic diesel as an option for a stock turbo Buick. If you're still concerned about ZDDP level, give Kriban $10 per oil change.
Mobil 1 10w-30 has 800 ppm Phosphorus (ZDDP)
Mobil 1 TDT 5w-40 has 1100 ppm Phosphorus (ZDDP)
Mobil 1 15w-50 has 1200 ppm Phosphorus (ZDDP)
Mobil 1 Racing 0w-30 has 1750 ppm Phosphorus (ZDDP), but is not recommended for street use (no detergents, I believe).
Brad Penn has 1400 ppm Phosphorus (ZDDP), but is not a Synthetic Oil.
Mobil 1 Oil Chart
Mobil 1 10w-30 has 800 ppm Phosphorus (ZDDP)
Mobil 1 TDT 5w-40 has 1100 ppm Phosphorus (ZDDP)
Mobil 1 15w-50 has 1200 ppm Phosphorus (ZDDP)
Mobil 1 Racing 0w-30 has 1750 ppm Phosphorus (ZDDP), but is not recommended for street use (no detergents, I believe).
Brad Penn has 1400 ppm Phosphorus (ZDDP), but is not a Synthetic Oil.
Mobil 1 Oil Chart
Modern DOHC 4 & 6 cyl. cars as mentioned more then likely have roller cams and do not need the additional addatives...wieght grades for different operating temps & turbos are a different issue. If you are running a roller cam pick your favorite oil, change regularly and be done with it. We are talking hi-performance motors with flat tappet cams where the current conventional & synthetic oils are a problem do to reduced ZDDP content. This is done to extend the life of catalytic converters but is a big problem with wiped cam shafts from reduced ZDDP. In this case run what you like and add ZDDP or run a Racing oil and no addative...pick a weight that fits your operating temp and again be done with it.
Diesel oils are going clean so the once high ZDDP diesel oils out there are also going away and no longer provide the needed ZDDP for a hi-performance flat tappet cammed motor.