I have a 1991 Mustang 2.3L and a 2003 Mustang 3.8L. I average 3K and 1.5K driving miles a year (mostly highway) respectively. The '91 Mustang has 70K original miles while the '03 has 28K on the ticker. With so little mileage each year, I only change the oil/filters once a year. Is it ok to use the Motorcraft oil filters, or should I invest in a high-end filter (i.e., Royal Purple, Amsoil) since the oil just sits in the filters for that length of time? I read somewhere (maybe on this site?) that once-a-year OCIs should instead include a filter with synthetic media, since this type is more durable than cellulose. Both Mustangs use the Motorcraft Synthetic Blend oil. Thanks in advance for any input, suggestions, or recommendations!