I was thinking of switching to Pennzoil's full synthetic 10w-30 from my Motorcraft 15W-40 I use now. Why? My truck is a 1996 Ford F-150, 302 V-8, now has 221,000 miles on it, I drive a 1000 miles a week. Want to extend the drain intervals from 3K-4K to like 6K. Right now the truck has been getting the oil done once a month since new. Maybe the Long Life 15w-40 might be better because of thickness for the bearing clearences. The truck gets the snot run out of it every day heavy loads, full throttle blasts, extended idle time, lots of abuse. Does not leak oil at all. Oh yeah, I forgot I also just treated the engine with Auto-RX yesterday with the fresh oil change, I will see how that work out, bought three bottles of it because of the high miles. So Johhny what would you reccomend for my application. Thanks!