Hello everyone. This is my first post. I wanted to see what you oil enthusiasts thought about my plan. I am planning on running Castrol Edge in my wifes Kia Sorrento and trying the extended drain interval. It says its good for 15K miles under normal driving conditions, which we fall under. Not alot of stop and go driving, no pulling trailers, hard accelerating, ect. We use it like a mini van really. I am using the Amsoil EA filter because its the only filter I could find rated for over 15K miles. I ordered a kit from Blackstone and planned on sending a sample at 7500 miles to see if they say it can go another 7500. Am I correct in asuming that I only have to pull the sample once, and from then on we know how many miles we can run on that engine, oil, filter combo? Is this not a good idea at all? I am also planning on trying it in my work truck, which does pull a trailer daily. Its get used pretty hard, so I was going to pull a sample at 3000 miles when I would normally change the oil, to see where it stands and decide on an interval there, but buying the more expensive oil I was hoping for at least 6-9K miles. What do you think, am I doing the right thing here? or am I asking for trouble?