ok i jus bought this 1989 corvette has the 5.7 tune port injection and it averaging 7.3 mpg and that under normal driving conditions. I dont know much about this car where would be a good place to start looking for the cause?

 

I have a 93 40th getting around 30 miles to gallon on highway
Thanks to some great advice from a corvette guy ,
I did a tune up and I use super 93 octane with a fuel injection cleaner each fill up
And I went from 12 miles to gallon to high 20's within 2-3 tanks of gas
A year later I'm up to around 30