I have 4 vehicles and 2 stay in the garage,sometimes i have to take them out and drive at least 20 miles or more once a week?Sometimes when i change oil at 3 months i have only 400 miles on it.I was wondering if it would hurt to use this in one of my daily drivers like a 88 caprice with 70,000 miles 4.3 V6?Or does the oil continue to degrade when used and sitting in a bottle? The 2 in the garage are a 94 suburban with 65,000 miles and a 99 Silverado with 15,000 miles.Just changed to Mobile one in each of these for the first time.The old oil is GTX 10-30. Thanks