i was running mobil delvac 1, full synth 5-40, but it's hard to find. i was just at walmart and saw they had mobil 1 for "turbo diesels", also a 5-40. i can't believe mobil would go to the effort to formulate two different 5-40 synth diesel oils to compete with themselves. is it the same stuff???

Im not sure on that, But i know the oil that comes in the gm bottol that is 15-40 is a mobil oil just not sure what one. I wana know what the diffrence is between mobil and mobil1

Yes, the new Mobil 1 turbo diesel, 5 -40 is the same as the old Delvac 1.