Do I need to use premium gas in my 96 Hoda Prelude?

The manual says yes--my pocket book says no. I live in California--I'm looking at $5 a gallon for premium, and as a starving college student, I just can't afford to do so. I've been using the midgrade, but now a lot of my local gas stations are dropping the price of regular as much as 20 cents lower than mid--which makes it tough doing even that. I don't want to screw up my engine (I can afford a new car even less than I can these gas prices), but, if I use the fuel additive ever 2-3 fill-ups and only shop at Chevron (which I have been told has the best quality gas, no matter what the grade), will I be ok...or am I severely lessening the life expectancy of my car?