In August I filled up my CTS-V with Mobil 1 EP 10w30 (first time using it) and promptly road tripped about 4200 miles in a week, 8-16 hours at a time. Just flat steady cruising. I was not surprised but after returning the oil was still very clean, completely full, and had no gas smell like it normally would (cam). I'm wondering how you think that kind of driving extends what would be my "normal" service interval. Usually I change the oil around 6,000 miles, it's 1/2-2/3 quart low, and is composed mostly of 5-20 mile trips with frequent spirited driving when the oil temp crosses 150. I'm past 7,000 miles now and the oil is still looking great. I feel like that 4,200 miles might be the equivalent of about 1500 of my regular miles. All the steady driving across a mostly flat states, very little load, very few restarts. Has to be easy on the additive package.