I just filled my 1999 Ford Ranger 4x4 4.0L with GC. How long of a drain can I reasonably get with the GC? The vehicle holds 5 quarts and I am using a Motorcraft FL-1A filter. I do about 10 to 15k a year mainly highway miles. I plan on doing a UOA at the end of the drain interval recommendation that I receive from you guys.