Dose it make your car run better or last long if you run full synthetic oil. 1996 Toyota Carmy V6

Both. It's a better oil.

Yes it is better oil. Synthetics were first developed by the US Air Force for use in jet, turbo jet, and turbo prop aircraft engines, even piston driven civilian aircraft engines They stand up to heat far better, last longer and simply lubricate better than petroleum oil..but beware, many oils labeled "synthetic" are blends that are marketed for cars, blended with petroleum oil. A true synthetic will cost as much as 3X more, but personally I think it's worth it.

PS changing from one to the other is fine but don't go back and forth...say you decide one day you don't want to spend the extra money when oil change time comes and you had synthetic but want to save a buck "this time"...don't do that and there are conflicting opinions on whether to add a quart of cheap oil to an engine one quart low or run it low on synthetic. Personally I would run it one quart low until I got the "right" oil