my 1998 f150 4.6 has been running on pennziol 5w30 (platinum full synthetic) for 3 months now but it has only 2200 miles,this is my first time using a full synthetic so should i change it or keep it longer the number im looking at is the months since i do a lot of short trips as you can see.maybe another way to look at it is that it may be a waste of money since i do lots of short trips and im so used to do 3k oil changes thats why next in line is regular pennzoil 5w30 with a wix oil filter