Its an "older truck" but has and oil life monitor, yet "synthetics were not around when it was made"????
Is this an aftermarket add on oil monitor that you installed? Anything that is new enough to have an oil life monitor was made when synthetic oil was around? Mobil 1 has been around since the 70s I think! And when I was working in a parts store in the early 00s every major manufacture had a synthetic oil as did our house brand of oil. At that time I don't think anything had oil life monitors , except maybe luxury cars...Mercedes or BMW??
Actually, it's a 2003 and I guess I just made an assumption that it was programmed for dino oil since nothing in the owners manual mentions synthetic oil. Also, since I usually drive right around the same number of miles every year, it seems that the oil life monitor on it keeps about the same settings through the year as it did when I first got it and was using dino oil. I've only been using Mobil 1 for the last 5-6 years.