mostly highway driving/cruising @ 70mph.
I'd expect that figure for city driving alone.

 

Kind of low mpg. Summer 70 to 80 mph highway: 23 mpg. Winter: 20- 23 mpg. (oxygenated fuel?).

 

i usuallly get 15mpg city butt, i got 24 coming from norcal-socal, what can we do to to improve??

 

Wow, I did 30 mpg last month on the highway. (60 mph, cruise, never above ~2800 rpm)

 

That's pretty remarkable.
I made about 400 miles on a tank a year ago (~26mpg) hauling 3 passengers and luggage.

I'm sure I need a tune-up, not that the cold weather is helping.

 

23-25 hwy and 20-21 city for me

 

These days have been extremely cold. Sooo cold it hurts. It was about 5-10 degrees during the day when suns out here in Troy NY. Tire pressure can change ur MPG dramatically. For example, when the temperature was around 30 degrees, I checked my tire pressure at about 30 PSI which is what the manual suggested for all the tires. And I got around 20 MPG local. The 20 degree drop of temperature dropped the tire pressure to 25 PSI. I think I lost about 4 MPG local because of that. Make a habit of checking your tire pressure. You can get one of those tire pressure gauge from Autozone or Pepboys for $1.99 or less. It saves you gas money in the long run