Is it safe to use a synthetic oil in my monte. Ive heard that synthetic oil is unusable in most older engines

 

Thats is BS. I switched my 1989 Chevy Silverado over to Full Synthetic at 185K. Its now got 223K on it and it runs awesome. In fact the synthetic oil really cleaned up some of the deposits that used to be inside the valve cover.

I always recommend synthetics.

Your Monte will be jsut fine with synthetic.