Been using 10w30 for 10,000 mile OCI in my Crown Vic for several years now. Excellent stuff, IMO.
My daily commute is 97 miles round trip. It's 90% highway with little traffic and few lights. Driving the same speed, keeping my tires properly inflated, air filter clean, etc, this oil consistently gives me about 4-5% higher MPG than Pennzoil and Valvoline. The car burns less than 2 cups per OCI.