I agree with Lippy in that in general older engines prefer dino
oil. Without knowing what the viscosity was for the prior
oil, it is hard to say anything about the current
oil pressure. Viscosity dictates oil pressure, not whether it is
synthetic or dino.
Lippy may be correct in that a drip or two of oil on the headers would cause some smell. Take a look at the ends of your side pipes, is there oil in the pipe, or are they clean/sooty? If you are burning more oil, you should see some evidence in the side pipes.