[ToySub1946]

My car is manual transmission.

Mileage varies greatly depending on just how fast you drive. Speeds over 70mph get you worse mileage.
I hate to say it, but keeping your speed down on freeways is the best way to save on gas. I don't do it, yet it's the best fuel saving trick.

I've gone 400 miles at freeway speeds before being on near empty....that's AFTER the gas light comes on. I'd say that's about as far as you'd wanna go. Most times you'd not wanna go more than 375 miles without having to worry.

I average 26-28mpg combined near home. I've averaged 31.5mpg driving a 3000 mile distance on almost all freeways. These figures are based on a calculator, not what the instrument cluster says. The average figure in instrument cluster is usually about 1 1/2 mpg too optimistic. I usually drive 7-8 mph over the limit. Limits are 65mph east coast, 75mph in the west.

Tank holds 13.2 gallons....and premium 91-93 octane is a must.

Our fuel here (always higher than east coast) currently up in price. $3.399 for premium. That's $.30 more than regular fuel here.
One time, on a trip, I paid $.60 a gallon more for premium than regular.

My suggestion: Buy a good used Prius.