In the past there has been some debate about whether or not one should use synthetic oil in an older car. Initially when synthetics first came out they had a higher detergent level than conventional oils, as a result it was argued that they cleaned out much of the build up that filled the teeny tiny cracks in the oil seals, thus releasing the “good crud” and causing micro leaks, which in turn led to larger leaks. Today this is largely unheard of, although there are those of us in the XT community who seem to have seen such leakage issues in the past. By and large, however, today it is not a concern.
Synthetic oil is excellent as a lubricant but it is rather expensive. It is often twice as expensive per unit than conventional oil. There are also blends of the two oil types available, but for the difference in cost, one might as well use full synthetic.
Bottom line: Sure, synthetic oil is great to use but it’s expensive. Conventional oil works well and it’s cheaper, but technically it isn’t as good as synthetic.