Triathlete, I have about 70-80 grand on my engine too. I am thinking about swapping to Mobil1 synthetic. Is it worth it? I can't seem to make up my mind. Opinions just go back and forth about this. I am not sure what to do, but I go on a 700 mile trip tomorrow morning and I'm 300 miles overdue for an oil change. It HAS to be done today. Help?