I have really learned a lot visiting this site over the last 3 weeks, and have confirmed some of my previous beliefs and blown some out of the water. Thanks. Here's my questions: Location and climate: Knoxville, TN 4 Season climate. 2 vehicles: 1- 1996 Ford Explorer V-6 4 liter push rod engine, 78000 miles and 800 miles into and AutoRx treatment.(Oil appears very similar to the way it looked when I started it, the dipstick is clean now.)It averages 7-9000 miles per year, mostly an 8 mile one way commute, more on the weekends. Maybe 4 trips a year averaging 500 miles round trip. I am planning on trying the GC after the flush with Wally World 5 qt Pennzoil 5W30 and extending oil change interval to ??? (have been changing every 3-3500 miles or 3 months, whichever came first,usually the 3 months.) 2- 2003 Dodge Ram 1500 with the Hemi engine (hold 7 1/2 Qts with the larger Ford Filter) 2950 miles on it, changed the break in oil out at 2000 miles to Valvoline Duro Blend 5W30, before I joined the forum. I will change oil according to Chryslers schedule during the warranty period. I will drive about 7500-9000 miles a year with daily commutes of 5 miles one way. More on the weekends and some trips over 500 miles RT. For the Hemi, I am leaning toward a good Dino, maybe the Pennzoil 5W30 and the larger Ford filter, changing at 4000 miles. I really am still clueless as to what weight oil to use, the bells aren't going off yet. Book says the same old 5W30-10W30 with the temp chart which basically means either here. I will most likey keep this truck more than 10 years. Your opinions and comments are appreciated.