I have what is possibly an odd question pertaining to oil. Our climate controlled garage contains a 2008, 4.6L Mustang and a 2008, 5.4L F150 (crew cab). I use Motorcraft 5w-20 synthetic blend and the corresponding Motorcraft filter at 5,000 mile oil change intervals. I presume this oil change interval is acceptable as it is the interval for special operating conditions. We drive short trips of 16 to 45 miles one way and occasionally the truck pulls a light trailer, but not often. Currently these vehicles are not driven daily and have accumulated only 3,000 miles each in the last 14 months. Does the oil need changed due to time sitting in the oil pan or is it still OK till the 5,000 mile mark?