I have always run synthetics (since 23k) on my jeep 2.5L 4banger and completed a auto rx clean and rinse in December 2004. I switched in 4 quarts of GC with 6 oz of Lube control and a Napa Gold Filter(my last stock sized one). I have added 2 Oz's of LC every 1k and am planning on running 6 month OCI's. I was going to do an April-OCT OCI and was going to change it out to start my routine. However I feel that 5-6k is a waste of decent oil. On the otherhand I would like to see how the oil has held up in my 5k oci. Should I change it out and just get into my 6 month OCI or should I wait and maybe go 7500 or even 10k? I know I can sample without changing all of my oil but that would mean cracking open a new bottle and oil putting in 1/4 bottle. I just don't want to deal with partial bottles.